Physical Geography 

'The earth wears away the mountains and 
fills up the valleys and if it had the power it 
would reduce the earth to a perfect sphere! 

The wave travels beneath the surface 1 of the sea, and leaves behind 
itself all the foam which is produced in front of it. 

The space of the surface of the water that intervenes between the 
waves as they come to the shore is polished and smooth; and this comes 
about because the greatest wave is swifter than the lesser waves of 
which it is made up [in the universal surface of the sea; and this 
greatest wave draws back the surface of the sea, and the first foam of 
the wave descends as it opens at the spot where the remainder is 
fleeing away. 

And the figure of the foam which then remains behind in the wave 
is always triangular, and its angle is made up of the first foam and 
that in front of the course where the wave first descended. 

c.a. 63 r. b 

The lowest parts of the world are the seas where all the rivers run. 

The river never ceases its movement until it reaches the sea; the sea 
therefore is the lowest part of the world. 

Water does not move from place to place unless it is drawn by a 
lower position. Lowness therefore serves as a magnet for water. 

c.a. 80 r. b 

Make a sketch to show where the shells are at Monte Mario. 

c.a. 92 v. c 

OF THE SEA WHICH GIRDLES THE EARTH 

I perceive that the surface of the earth was from of old entirely filled 
up and covered over in its level plains by the salt waters, and that the 
1 la pelle, literally 'the skin' of the sea. 

315 

316 PHYSICAL GEOGRAPHY 

mountains, the bones of the earth, with their wide bases, penetrated 
and towered up amid the air, covered over and clad with much high- 
lying soil. Subsequently the incessant rains have caused the rivers to 
increase and by repeated washing have stripped bare part of the lofty 
summits of these mountains, leaving the site of the earth, so that the 
rock finds itself exposed to the air, and the earth has departed from 
these places. And the earth from off the slopes and the lofty summits 
of the mountains has already descended to their bases, and has raised 
the floors of the seas which encircle these bases, and caused the plain 
to be uncovered, and in some parts has driven away the seas from there 
over a great distance. c.a. 126 v. b 

DOUBT 

Here a doubt arises, and that is as to whether the Flood which came 
in the time of Noah was universal or not, and this would seem not to 
have been the case for the reasons which will now be given. We have it 
in the Bible that the said Flood was caused by forty days and forty 
nights of continuous and universal rain, and that this rain rose ten 
cubits above the highest mountain in the world. But consequently if it 
had been the case that the rain was universal it would have formed in 
itself a covering around our globe which is spherical in shape; and a 
sphere has every part of its circumference equally distant from its 
centre, and therefore on the sphere of water finding itself in the afore- 
said condition, it becomes impossible for the water on its surface to 
move, since water does not move of its own accord unless to descend. 
How then did the waters of so great a Flood depart if it is proved that 
they had no power of motion? If it departed, how did it move, unless 
it went upwards? At this point natural causes fail us, and therefore in 
order to resolve such a doubt we must needs either call in a miracle to 
our aid or else say that all this water was evaporated by the heat of 
the sun. c.a. 155 r. b 

[Diagram] 

Three is the number of the winds which bend the rivers to the west 
as they discharge themselves into the Mediterranean Sea on the shores 
that face south. This is proved as follows: the sand that is driven by 
the winds into the water is no longer subject to the winds, through 

PHYSICAL GEOGRAPHY 317 

being weighed down by the water which covers it over and forms a 
screen tor it against these winds. 

Therefore the river /; m which ilows into the sea will half way in its 
course make a beginning of a movement to the west, when it feels the 
breath of the winds known as Greco, Levante and Scirocco, which at 
various times set the dry sand of the shore spinning, and hurl it into 
the sea, where it becomes submerged and settles upon the bed of the 
sea. But the north wind called Greco throws it to the south-west, and 
the Scirocco throws it to the north-west. But the southern waves strik- 
ing on the shore throw this sand back towards the river, and the river 
strikes it back towards the sea; and when the waves struck back from 
the shore come to an encounter with the waves advancing to the shore 
the movement of these waves then ceases because the power of their 
movement is lacking. Therefore the sand having made the water turbid 
descends to the bottom, and it is this same sand which forms itself into 
a bank and bends in a westerly direction the aforesaid river. Why does 
it not bend the course of the river to the east as well as to the west? 
Because the sea has been proved to run to the west and not to the east. 

Let us therefore make a bridge as wide and low as the shore out of 
large planks. c.a. 167 v. a 

The water wears away the mountains and fills up the valleys, and if 
it had the power it would reduce the earth to a perfect sphere. 

c.a. 185 v. c 

INSTANCES AND DEDUCTIONS AS TO THE 
EARTH'S INCREASE 

Take a vase, fill it full of pure earth, and set it up on a roof. You will 
see how immediately the green herbs will begin to shoot up, and how 
these, when fully grown, will cast their various seeds; and after the 
children have thus fallen at the feet of their parents, you will see the 
herbs having cast their seeds, becoming withered and falling back again 
to the earth, and w r ithin a short time becoming changed into the earth's 
substance and giving it increase; after this you will see the seeds spring- 
ing up and passing through the same course, and so you wall always see 
the successive generations after completing their natural course, by their 
death and corruption giving increase to the earth. And if you let ten 

318 PHYSICAL GEOGRAPHY 

years elapse and then measure the increase in the soil, you will be able 
to discover how much the earth in general has increased, and then by 
multiplying you will see how great has been the increase of the earth in 
the world during a thousand years. Some may say that this instance of 
the vase which I have mentioned does not justify the deduction based 
upon it, because one sees in the case of these vases that for the prize of 
the flowers that are looked for a part of the soil is frequently taken 
away, and its place is filled up with new rich soil; and I reply to them 
that as the soil which is added there is a blend of rich fat substances 
and broken bits of all sorts of things it cannot be said to be pure earth, 
and this mass of substances decaying and so losing in part their shape 
becomes changed into a rich ooze, which feeds the roots of the plants 
above them; and this is the reason why it may appear to you that the 
earth is lessened; but if you allow the plants that grow in it to die, and 
their seeds to spring up, then in time you will behold its increase. 

For do you not perceive how, among the high mountains, the walls 
of ancient and ruined cities are being covered over and concealed by 
the earth's increase? 

Nay, have you not seen how on the rocky summits of the mountains 
the live stone itself has in course of time swallowed up by its growth 
some column which it supported, and stripping it bare as with shears 
and grasping it tightly, has left the impress of its fluted form in the 
living rock? c.a. 265 r. a 

When mountains fall headlong over hollow places they shut in the 
air within their caverns, and this air, in order to escape, breaks through 
the earth, and so produces earthquakes. 

My opponent says this cannot be the case, for either the whole 
mountain which covers the cavern falls or else only the inner part of it; 
and if the whole falls, then the compressed air escapes through the 
opening of the cave which is uncovered, while if only the inner part 
falls then the compressed air escapes into the vacuum which is left by 
the falling earth. c.a. 289 v. b 

Similarly the movements of the waters running through all the pas- 
sages of the sterile earth are its life-giving force. And just as the mois- 
ture spread through the vine rises up and pours through the severed 
members, (the utmost heights of the mountains through the severed 

PHYSICAL GEOGRAPHY 319 

veins), so it is with the water which rises to a height and pours through 
the chasms in the topmost heights of the mountains. 

In the same way the waters from the base rise to a height, pouring 
through the chasms in the topmost heights of the highest mountains. 

And as the moisture which pours through the severed vine desires 
only the centre of the earth and moves towards it, so the waters pour- 
ing from the heights of the mountains move of their own free will 
towards this centre. 

And as the water from the severed vine falling down upon its roots 
and penetrating into these raises itself up to a height and pours itself 
out again at the very place where the cutting was, so the water falling 
from the summits of the mountains and penetrating through the pas- 
sages of the earth returns upwards. c.a. 309 v. a 

The surface of the Red Sea is on a level with the Ocean. 

This made the Mediterranean light both in the bed which is lowered 
and in the surface where formerly was the water. 

Lacking the weight of the waters of the Mediterranean which had 
been diminished the earth rose and changed in itself its centre of 
gravity. 

The waters of the sea which descend into the Ocean from the Medi- 
terranean Sea have through the force of their impact on the bottom 
hollowed out this bed considerably beneath the surface of this Ocean; 
and in their fall this hollowing out has withdrawn itself to the point at 
which it arrives at the end of the channel of Gades, and there it is 
visible to-day. 

A mountain may have fallen and blocked the mouth of the Red Sea 
and prevented the outlet to the Mediterranean, and thus swirling in a 
flood this sea will have as its outlet the passage between the mountains 
of Gades, for in the same way we have seen in our time a mountain 
fall seven miles and block up a valley and make a lake; and thus the 
greater number of the lakes were made by mountains, as the lake of 
Garda, of Como and Lugano and Lake Maggiore. . . . 

All the plains which lie between the seas and the mountains were 
once covered by the salt waters. 

Every valley has been made by its river, and the proportion between 
valleys is the same as that between rivers. 

320 PHYSICAL GEOGRAPHY 

The greatest river in the world is the Mediterranean which is a river 
that moves from the source of the Nile to the Western Ocean. 

c.a. 328 v. b 

The water given to the Mediterranean by rain and rivers is restored 
to the Ocean through the straits of Gades [Gibraltar], with so much 
less water in proportion as the springs are beneficent to it and the sea 
evaporates it. 

And this excess is the cause of the ebb and flow, because in the flow 
the Mediterranean is swollen up by the Ocean and this turns back and 
ebbs away through the Mediterranean which discharges it. 

c.a. 353 v. c 

Just as the snow as it falls in flakes upon various rounded objects 
covers them with itself but with as many varying degrees of thickness 
as there are variations in the curves of this roundness, so the earth, 
borne by the floods of the rivers after the mass of the waters, descends 
upon the various rounded objects which are at the bottom of the waters 
and covers these with itself in the manner shown above, c.a. 383 v. 

OF THE CENTRE OF THE OCEAN 

The centre of the sphere of water is the true centre of the orb of our 
world which is compounded of land and water in the shape of a sphere. 
But if you wish to find the centre of the element of the earth this is 
situated at a point equidistant from the surface of the ocean and not 
equidistant from the surface of the earth. For it is easy to understand 
that this globe of the earth has no perfect roundness whatever except in 
those parts in which are the sea or lakes or other surfaces of still water; 
and every part of the land which rises above the water is farther 
removed from the centre. a 58 v. 

OF THE MOVEMENT OF AIR AND WATER 

This air which bounds and continually moves upon this terrestrial 
machine is mixed with moisture similar to that with which the earth is 
compounded, and the excess of this moisture falls back continually 
upon the earth once in twenty-four hours and then springs back raised 

PHYSICAL GEOGRAPHY 321 

■j little by the heat of the sun and sustained by it so long as it remains 
in our hemisphere. Then being left abandoned by it at its departure 
and still having weight it falls back on the earth. 

In summer this moisture is called dew and in winter as the cold 
condenses it and freezes it it is called hoar frost. c 6 r. 

OF HOW THE SEA CHANGES THE WEIGHT OF 
THE EARTH 

The shells of oysters and other similar creatures which are born in 
the mud of the sea testify to us of the change in the earth round the 
centre of our elements. This is proved as follows: — the mighty rivers 
always flow turbid because of the earth stirred up in them through the 
friction of their waters upon their bed and against the banks; and this 
process of destruction uncovers the tops of the ridges formed by the 
layers of these shells, which are embedded in the mud of the sea where 
they were born when the salt waters covered them. And these same 
ridges were from time to time covered over by varying thicknesses of 
mud which had been brought down to the sea by the rivers in floods 
of varying magnitude; and in this way these shells remained walled up 
and dead beneath this mud, which became raised to such a height that 
the bed of the sea emerged into the air. 

And now these beds are of so great a height that they have become 
hills or lofty mountains, and the rivers which wear away the sides of 
these mountains lay bare the strata of the shells, and so the light surface 
of the earth is continually raised, and the antipodes draw nearer to the 
centre of the earth, and the ancient beds of the sea become chains of 
mountains. e 4 v. 

The destruction of marshes will be brought about when turbid rivers 
flow into them. 

This is proved by the fact that where the river flows swiftly it washes 
away the soil, and where it delays there it leaves its deposit, and both 
for this reason and because water never travels so slowly in rivers as it 
does in the marshes of the valleys the movement of the waters there is 
imperceptible. But in these marshes the river has to enter through a 
long narrow winding channel, and it has to flow out over a large area 

322 PHYSICAL GEOGRAPHY 

of but little depth; and this is necessary because the water flowing in 
the river is thicker and more laden with earth in the lower than in the 
upper part; and the sluggish water of the marshes also is the same, 
but the variation between the lightness and heaviness of the upper and 
lower waters of the marshes far exceeds that in the currents of the 
rivers, in which the lightness of the upper part differs but little from 
the heaviness of the part below. 

So the conclusion is that the marsh will be destroyed because it is 
receiving turbid water below, while above, on the opposite side of the 
same marsh, only clear water is flowing out; and consequently the bed 
of the marsh will of necessity be raised by means of the soil which is 
being continually discharged into it. e 5 r. 

How by running waters one should conduct the soil of the mountains 
into marshy valleys and so render them fertile and purify the sur- 
rounding air: 

The ramifications of the canals which are led from the high hills 
according to their natural course are those which in their changes carry 
the soil from these hills to the low marshes, filling them up with earth 
and rendering them fertile. 

Let a be the main stream which enters the marshes at b f s; let the 
canal start from the height of the hills a c n, from which suppose vari- 
ous branches to have fallen, changing it where it is all united into 
different places, and thus their fury tears away the soil and after they 
have run their course they deposit it in the low swamps; and thus you 
will be able to change so much the fall of the whole canal, abounding 
as it does in water, that you will have levelled the soil left uncovered 
from these marshes. f 14 r. 

Why pools are formed near the sea, and why their great floods are 
poured into the sea through so narrow a channel, upon the sides of 
which between the pool and the sea so great a bank is formed: 

The storms of the sea cast up on to the shore a great quantity of sand, 
and this is heaped up all along the shore both at the mouth of the pool 
and elsewhere; and as the storm ceases the mouth of the pool remains 
closed by the aforesaid matter thrown up by the sea. And as the water 
that the pool receives from the neighbouring rivers cannot find any 
other exit it proceeds to rise and acquire weight and power; and there- 

PHYSICAL GEOGRAPHY 323 

fore it either bursts through the bank interposed between it and the sea 
or flows over it and with its outpouring wears away as much of the 
bank as it touches, pursuing its course until it has cleared out of its 
path all the matter that impeded its necessary dispersion. 

Moreover it only consumes what is necessary; at first it is very large 
because the water that flows towards where the mouth should be is 
clear, and at the end the course of the water becomes contracted, be- 
cause it has become thicker as it acquires depth; and this is the reason 
why such outlet from the pools to the sea is always narrow, f 40 v. 

OF THE WAVES 

Sometimes the waves are swifter than the wind, and sometimes the 
wind is much swifter than the wave; the ships prove this upon the sea. 
The waves can be swifter than the wind through having been com- 
menced by the great winds, the wind then having ceased and the wave 
having still preserved a great impetus. f 48 v. 

One asks whether a river which passes through a lake changes the 
uniform distance at which the surface of this lake was from the centre 
of the earth before this river passed through the said lake. 

This is an interesting question; and one shows that this surface dis- 
turbs the uniformity of its distance from the centre of the earth in 
order to give a passage to the said river, by the fourth [rule], which 
shows that water does not move unless to descend. And here it is neces- 
sary to understand whether the exit of the river has a width equal to 
that of the entrance and if this is so it is necessary that the water be of 
uniform course, by the seventh [rule], which shows that the movement 
of every river in an equal time gives to every part of its length an equal 
weight of water. Now if the river emitted water which required a drop 
of a braccio in a mile, the width of the exit being as has been said equal 
to the width of the entrance, it would be necessary that all the river 
which passes through the lake should also have a drop of one braccio 
per mile, and consequently the water of this lake would have its surface 
at a varying distance from the centre of the earth. But the water will 
have this course. . . . 

That part of the water of the lake will be of slowest movement which 

324 PHYSICAL GEOGRAPHY 

finds itself farthest removed from the shortest line from the entrance to 
the exit of the river which passes through this lake. 

Here it follows that the Sea of Azov which borders upon the Don is 
the highest part of the Mediterranean Sea; and it is three thousand five 
hundred miles distant from the straits of Gibraltar, as is shown by the 
navigators' chart; and it has a descent of three thousand five hundred 
braccia, that is a mile and a sixth, this sea consequently being higher 
than any mountain that there is in the west. f 68 r. and v. 

OF THE WIND 

Since the eddies of the winds are below and above as well as cross- 
wise the countryfolk cannot tell what wind it is that is blowing, that is 
those who dwell under the hills by the sea shores do not know if the 
wind is from an eddy or if it is the straight wind. 

The wind that strikes upon the sea coasts or borders or sides of the 
mountains raises itself up to the summit where it presses itself against 
the course of the other straight wind, and then it spreads itself out 
moistening the opposite. ... i 130 [82] v. 

Why the thunder lasts for a longer time than that which causes it; 
and why, immediately on its creation, the lightning becomes visible to 
the eye, while the thunder requires time to travel, after the manner of a 
wave, and makes the loudest noise when it meets with most resistance. 

k no [30] v. 

WINDS AND THUNDERBOLTS 

The winds which rise from the cloud continue in movement; in such 
a way that the more they move the farther they rise in the lighter air 
because they are less impeded there. And if they meet each other they 
leap back, and it is in these encounters that thunderbolts are produced. 

If the wind originates at a low altitude, what is it that drives it more 
to the east than to the west ? k 113 [33] r. 

[Watery sphere and centre of world] 

The surface of the watery sphere is always more remote from the 
centre of the world: 

PHYSICAL GEOGRAPHY 325 

This comes about by reason of the soil brought by the inundations 

of turbid rivers. These deposit the soil which causes their turbidity on 
the shores of the ocean and so narrow the sea beach; beside this they 
raise their bed and so of necessity the surface of this element comes to 
be raised. 

The centre of the world continually changes its position in the body 
of the earth fleeing towards our hemisphere. 

This is shown by the above-mentioned soil which is continually car- 
ried away from the declivities or sides of the mountains and borne to 
the seas; the more it is carried away from there the more it becomes 
lightened and as a consequence the more it becomes heavy where this 
soil is deposited by the ocean waves, wherefore it is necessary that such 
centre changes its position. l 13 v. 

[Surface of the earth and centre of gravity] 

That part of the surface of any heavy body will become more distant 
from the centre of its gravity which becomes of greater lightness. 

The earth therefore, the element by which the rivers carry away the 
slopes of the mountains and bear them to the sea, is the place from 
which such gravity is removed; it will make itself lighter and in conse- 
quence will make itself more remote from the centre of the gravity of 
the earth, that is from the centre of the universe which is always con- 
centric with the centre of the gravity of the earth. l 17 r. 

[Changes in mountains and valleys] 

The summits of the mountains in course of time rise continually. 

The opposite sides of the mountains always approach one another. 

The depths of the valleys which are above the watery sphere in 
course of time constantly draw near to the centre of the world. 

During the same period of time the valleys sink much more than 
the mountains rise. 

The bases of the mountains are always drawing closer together. 

As the valley grows deeper so its sides become worn away in a shorter 
space of time. l 76 r. 

[Cosmography of Ptolemy] 

A line commenced at one extremity of the world may still be parallel 
and equidistant to another line commenced at the opposite side of the 

326 PHYSICAL GEOGRAPHY 

world, as Ptolemy shows in his Cosmography when he shows that cities 
situated in the opposite extremities of the earth are in the same parallel. 

m 5 v. 
[Water upon sand] 

Why as smooth sand is formed of grains uneven in shape and size 
the water which flows above them drives these grains with varying 
degrees of movement ? Just as the bodies that vary in weight and shape 
make different movements in the still air so do the air and the water as 
they move among still bodies. And this is why the sand loses its smooth- 
ness by the movement of the water that passes over it. And the moved 
water performs the same function upon the sand as the moved air does 
upon the water. And if you prove that the bed of the flat sand makes 
its waves and becomes uneven through the unevenness of its granules, 
and that such unevenness could not exist on the surface of the water 
which is a smitten and uniform body, I will maintain that the air is full 
of parts which have a movement that is not uniform and therefore the 
parts moved by the contact of the air move without uniformity. 

m 41 r. 

The cause which makes water move in the springs contrary to the 
natural course of its gravity works in the same way in all the humours 
in all species of animated bodies. And just as the blood from below 
surges up and then falls back should a vein burst in the forehead, so 
the water rises from the lowest depth of the sea to the summits of the 
mountains, and there, finding the springs burst open, is poured out 
through them and returns to the depths of the sea. Have you ever seen 
how the water that drips from the severed branches of the vine and 
falls back upon its roots penetrates these and so rises up anew? Thus 
it is with the water that falls back into the sea, for it penetrates through 
the pores of the earth and having returned into the power of its mover, 
whence it rises anew with violence and descends in its accustomed 
course, it then returns. Thus adhering together and united in continual 
revolution it goes moving round backwards and forwards; at times it 
all rises together with fortuitous movement, at times descends in 
natural liberty. Thus moving up and down, backwards and forwards, it 
never rests in quiet either in its course or in its own substance: and as 
the mirror is changed to the colour of the objects which pass before it, 

PHYSICAL GEOGRAPHY 327 

it has nothing of itself but moves or takes everything, and is changed to 
as many different natures as the places are different through which it 
passes. b.m. 58 v. 

That principle which moves the watery humours contrary to the 
natural course of their gravity in all living species moves the water 
also through the springs in the ground, and with continual solicitude 
renders aid in all those places in which necessity teaches it. And that 
which is seen falling down from high places and forming the com- 
mencement of the course of every river, acts in the same manner as the 
blood that rises up from the lower part and pours itself away through 
a cleft in the forehead. b.m. 59 r. 

From the two lines of shells one must needs suppose that the earth 
in disdain plunged beneath the sea and so formed the first layer and 
that the Flood afterwards formed the second. b.m. 156 v. 

How the rivers widen the valleys and wear away the roots of the 
mountains along their sides: 

The windings which the rivers make through their valleys as they 
leap back from one mountain to another cause the bank to form curves, 
and these curves move with the current of the water and in course of 
time seek out the whole valley, unless they are checked by the fact of it 
becoming increased in length and depth and diminished in breadth. 

b.m. 168 v. 

And as from the lower part of the vine the water rises to the severed 
branches, and falls back upon its roots and by penetrating these rises 
up again to the point where they are broken and falls back afresh, even 
so does the water. 

So from the lowest depth of the sea the water raises itself and rises to 
the summits of the mountains, and as the water pours through the 
severed branches of the vine and falls back upon its roots, penetrating 
them, even so does the water which. . . . b.m. 233 r. 

So does the water which is moved from the deep sea up to the sum- 
mits of the mountains, and through the burst veins it falls down again 
to the shallows of the sea, and so rises again to the height where it burst 
through, and then returns in the same descent. Thus proceeding alter* 

328 PHYSICAL GEOGRAPHY 

nately upwards and downwards at times it obeys its own desire at times 
that of the body in which it is pent. b.m. 233 v. 

Every heap of sand whether it be on level ground or sloping will 
have its base twice the length of its axis. Forster 11 16 r. 

OF THE SEA 

If the water becomes so salt through the earth being burnt up by 
the sun it should follow that when the earth is boiled in water this 
water becomes salt. Quaderni 11 19 r. 

[Influence of sun and moon on tides] 

That power shows itself greater which is impressed upon a lesser 
resistance. This conclusion is universal and we may apply it to the flow 
and ebb in order to prove that the sun or moon impresses itself more 
on its object, that is on the waters, when these are of less depth. Conse- 
quently the shallow waters of swamps ought to receive with greater 
potency the cause of the flow and ebb, than the great depths of the 
ocean. Quaderni 11 22 v. 

[Filling of footprints in sand] 

When the foot is drawn up out of wet sand the water runs back right 
to the surface of the sand, and this occurs because the water which is 
mingled with the sand is quicker to fill up the vacuum left by the foot 
than the sand is, and the air would be even quicker if it could enter; 
but the wet sand always keeps the way closed up by which the leg 
entered the sand, and so prevents the air from entering to fill up the 
vacuum. Quaderni iv 15 r. 

How the valleys were formerly in great part covered by lakes be- 
cause their soil always forms a bank for rivers, and by seas which after- 
wards through the unceasing action of the rivers that form the store of 
water that is in the mfountains], cut through the mountains; and the 
rivers in their wandering courses carried away the wide open plains 
enclosed by the mountains; and the cuttings of the mountains are per- 
ceptible from the strata of the rocks which correspond to the sections 
made by the said courses of the rivers : 

The Haemus range which crosses Thrace and Dardania and joins on 

PHYSICAL GEOGRAPHY $29 

the west the Sardonius range as it proceeds towards the west changes 
the name of Sardus to Rcbi as it approaches Dalmatia, and then contin- 
uing towards the west crosses Illyria now called Slavonia, and changes 
the name of Rebi to Albanus, and still continuing westward changes it 
to the Ocra range. 

To the north and south above Istria it is named Caruancas (Caru- 
sadiusr), and to the west above Italy it unites with the Adula range 
where the Danube 1 rises, which flows for a course of fifteen hundred 
miles and for about a thousand miles in the most direct line; and for 
just as far or thereabouts the spur of the Adula range is changed to 
the names of the mountains already mentioned. 

To the north stands the Carpathian range which encloses the breadth 
of the valley of the Danube which as I have stated stretches eastwards 
for a distance of about a thousand miles and has a width of sometimes 
two hundred and sometimes three hundred miles. Through the midst 
of it flows the Danube, the first river of Europe in magnitude, and this 
Danube as it flows leaves on the south Austria and Albania and on the 
north Bavaria, Poland, Hungary, Wallachia and Bosnia. The Danube 
or as it is called the Donau then flows into the Black Sea which used 
to extend almost as far as Austria and covered all the plain where 
to-day the Danube flows; and the sign of this is shown by the oysters 
and cockleshells and scollops and bones of great fishes which are still 
found in many places on the high slopes of the said mountains; and 
this sea was created by the filling up of the spurs of the Adula range 
which extend to the east and unite with the spurs of the Taurus range 
extending to the west. And near Bithynia the waters of this Black Sea 
discharged themselves into the Propontis, falling into the Aegean Sea, 
that is the Mediterranean Sea, where at the end of their long course the 
spurs of the Adula range are severed from those of the Taurus range, 
and the Black Sea sank down and laid bare the valley of the Danube 
with the above-named provinces, and the whole of Asia Minor beyond 
the Taurus range to the north, and the plain which stretches from the 
Caucasus to the Black Sea to the west, and the plain of Tanais (the 
Don) this side of the Ural mountains that is at their feet. 

So the Black Sea must have sunk about a thousand braccia to uncover 
such vast plains. Leic. 1 v. 

X MS. has Rhine. 

330 PHYSICAL GEOGRAPHY 

In this work of yours you have first to prove how the shells at a height 
of a thousand braccia were not carried there by the Deluge, because 
they are seen at one and the same level, and mountains also are seen 
which considerably exceed this level, and to enquire whether the Del- 
uge was caused by rain or by the sea rising in a swirling flood; and 
then you have to show that neither by rain which makes the rivers 
rise in flood nor by the swelling up of the sea could the shells being 
heavy things be driven by the sea up the mountains or be thrown there 
by the rivers contrary to the course of their waters. Leic. 3 r. 

When a river flows out from among mountains it deposits a great 
quantity of large stones in its gravelly bed, and these stones still retain 
some part of their angles and sides; and as it proceeds on its course it 
carries with it the lesser stones with angles more worn away, and so 
the large stones become smaller; and farther on it deposits first coarse 
and then fine gravel, and after this big and then small shingle, and 
after this follows sand at first coarse and then more fine; and thus 
continuing the water turbid with shingle and sand reaches the sea. 

The shingle is deposited over the shores of the sea by the backwash 
of the salt waves, until at last the sand becomes so fine as to seem al- 
most like water. Nor does this remain upon the sea shores but goes 
back with the wave by reason of its lightness, being formed of rotting 
leaves and other things of extreme lightness; and consequently being 
as has been said almost of the nature of water in time of calm weather 
it drops down and settles at the bottom of the sea, where by reason 
of its fineness it becomes compressed and resists the waves which pass 
above it on account of its smoothness; and in this shells are found and 
this is the white earth that is used for making jugs. Leic. 6 v. 

OF THE FLOOD AND OF MARINE SHELLS 

If you should say that the shells which are visible at the present time 
within the borders of Italy, far away from the sea and at great 
heights, are due to the Flood having deposited them there, I reply that, 
granting this Flood to have risen seven cubits above the highest moun- 
tain, as he has written who measured it, these shells which always in- 
habit near the shores of the sea ought to be found lying on the moun- 

PHYSICAL GEOGRAPHY 331 

tain sides, and not at so short a distance above their bases, and all at 
the same level, layer upon layer. 

Should you say also that the nature of these shells causes them to 
keep near the edge of the sea, and that as the sea rose in height the 
shells left their former place and followed the rising waters up to their 
highest level: — to this I reply {that in forty days the shells cannot 
travel x ) that the cockle is a creature incapable when out of water of 
more rapid movement than the snail, or is even somewhat slower, 
since it does not swim, but makes a furrow in the sand, and support- 
ing itself by means of the sides of this furrow will travel between three 
and four braccia in a day; and therefore with such a rate of motion it 
would not have travelled from the Adriatic Sea as far as Monferrato in 
Lombardy, a distance of two hundred and fifty miles, in forty days, — 
as he has said who kept a record of this time. 

And if you say that the waves carried them there, — they could not 
move by reason of their weight except upon their base. And if you do 
not grant me this, at any rate allow that they must have remained on 
the tops of the highest mountains, and in the lakes which are shut in 
among the mountains, such as the lake of Lario or Como, and Lake 
Maggiore 2 , and that of Fiesole and of Perugia and others. 

The water of the contingent seas forms the sphere of the water which 
has for the centre of its surface the centre of the world but not as the 
centre of its gravity, because in many places it is of great depth and in 
many of small depth, and for this reason as it is not of uniform thick- 
ness it is not of uniform weight. But merely because that thing is 
higher which is more remote from the centre of the world, therefore 
this surface not being in movement cannot remain in any place higher 
in one part than in another, because the highest part of the water al- 
ways seeks to fill up with itself the part of it which is lower. 

If the Flood passed as has been said, above the mountains of our 
hemisphere, without doubt it made the gravity of this our habitable 
part greater than that of the antipodes, and as a consequence it brought 
it nearer to the centre of the world than it was at first; and the part 
opposite was removed farther away from this centre, for which reason 

1 Words crossed out in MS. 

2 MS. 'come lago di Lario, e'l Maggiore, e di Como'. Larius was however the Latin 
ivame for Lake Como. 

332 PHYSICAL GEOGRAPHY 

the aforesaid Flood submerged more than would have been sub- 
merged if such gravity had not been acquired by it on this side. 

If you should say that the shells were empty and dead when carried 
by the waves, I reply that where the dead ones went the living were 
not far distant, and in these mountains are found all living ones, for 
they are known by the shells being in pairs, and by their being in a row 
without any dead, and a little higher up is the place where all the dead 
with their shells separated have been cast up by the waves. Near to 
there the rivers plunged into the sea in great depth; like the Arno 
which fell from the Gonfolina near to Monte Lupo and there left 
gravel deposits, and these are still to be seen welded together, forming 
of various kinds of stones from different localities and of varying colour 
and hardness one concrete mass. And a little farther on, where the 
river turns towards Castel Fiorentino the hardening of the sand has 
formed tufa stone; and below this it has deposited the mud in which 
the shells lived; and this has risen in layers according as the floods of 
the turbid Arno were poured into this sea, and so from time to time 
the bed of the sea was raised. 

This has caused these shells to be produced in pairs, as is shown in 
the cutting of Colle Gonzoli, made sheer by the river Arno which 
wears away its base, for in this cutting the aforesaid layers of shells 
may be seen distinctly in the bluish clay, and there may be found 
various things from the sea. 

And the earth of our hemisphere became raised up more than it was 
before as by degrees it became lightened of the water that flowed away 
from it through the straits of Gibraltar; and it was raised so much the 
more because the weight of the water which flowed away from it was 
added to that of the earth that was turned to the other hemisphere. 

And if the shells had been in the turbid water of a deluge they would 
be found mixed up and separated one from another, amid the mud, 
and not in regular rows in layers as we see them in our own times. 

Leic. 8 v. 

As for those who say that these shells are found to exist over a wide 
area having been created at a distance from the sea by the nature of the 
locality and the disposition of the heavens, which moves and influences 
the place to such a creation of animal life, to these it may be answered 

PHYSICAL GEOGRAPHY 333 

that granted such an Influence over these animals it could not happen 

that they were in one line except in the case of animals of the same 
species and age; and not the old with the young, nor one with an outer 
covering and another without its covering, 1 nor one broken and an- 
other whole, one filled with sea sand, and the fragments great and 
small of others inside the whole shells which stand gaping open; nor 
the claws of crabs without the rest of their bodies; nor with the shells 
of other species fastened on to them like animals crawling over them 
and leaving the mark of their track on the outside where it has eaten 
its way like a worm in wood; nor would there be found among 
them bones and fishes' teeth which some call arrows and others ser- 
pents' tongues; nor would so many parts of different animals be found 
joined together, unless they had been thrown up there upon the borders 
of the sea. 

And the Flood would not have carried them there because things 
heavier than water do not float upon the surface of the water, and the 
aforesaid things could not be at such heights unless they had been car- 
ried there floating on the waves, and that is impossible on account of 
their weight. 

Where the valleys have never been covered by the salt waters of the 
sea there the shells are never found; as is plainly visible in the great 
valley of the Arno above Gonfolina, a rock which was once united with 
Monte Albano in the form of a very high bank. This kept the river 
dammed up in such a way that before it could empty itself into the 
sea which was afterwards at the foot of this rock it formed two large 
lakes, the first of which is where we now see the city of Florence 
flourish together with Prato and Pistoia; and Monte Albano followed 
the rest of the bank down to where now stands Serravalle. In the up- 
per part of the Val d'Arno as far as Arezzo a second lake was formed 
and this emptied its waters into the above-mentioned lake. It was shut 
in at about where now we see Girone, and it filled all the valley above 
for a distance of forty miles. This valley received upon its base all the 
earth carried down by the turbid waters and it is still to be seen at its 
maximum height at the foot of Prato Magno for there the rivers have 
not worn it away. 

Within this soil may be seen the deep cuttings of the rivers which 

1 MS. e l'altro essere colla sua copritura. 

334 PHYSICAL GEOGRAPHY 

have passed there in their descent from the great mountain of Prato 
Magno; in which cuttings there are no traces visible of any shells or of 
marine earth. 

This lake was joined to that of Perugia. 

A great quantity of shells may be seen where the rivers empty them- 
selves into the sea, because in such places the water is not very salt on 
account of the mixture of the fresh water which unites with it. A proof 
of this is to be seen where the Apennines once emptied their rivers into 
the waters of the Adriatic, for there among the mountains in most 
parts a great quantity of shells are visible together with bluish marine 
clay; and all the rocks which are broken away in such places are found 
to be full of shells. 

We know that the Arno did the same when it fell from the rock of 
Gonfolina into the sea which was not very far below it, because in those 
times it must have stood higher than the top of San Miniato al Tedesco, 
since in the highest summits of this [mountain] one sees the rocks full 
of shells and oysters within its banks; the shells did not extend in the 
direction of Val di Nievole because the fresh waters of the Arno did 
not extend so far. 

How the shells were not carried from the sea by the Deluge, because 
the waters which came from the earth to the sea although they drew 
the sea towards the earth were those which smote its base, because the 
water which comes from the earth has a stronger current than that of 
the sea, and as a consequence is more powerful and enters beneath the 
other water of the sea, and stirs up the bottom and carries with it all 
the movable objects which are to be found in it such as the above- 
mentioned shells and other like things; and as the water which comes 
from the land is muddier than that of the sea it is so much the more 
powerful and heavier than it. I do not see therefore in what way the 
said shells could have come to be so far inland unless they had been 
born there. 

If you should tell me that the river Loire which passes through 
France spreads itself over more than eighty miles of country when the 
sea is increased, because the country forms a great plain and the sea 
rises about twenty braccia, and that shells are sometimes found in this 
plain at a distance of eighty miles from the sea, the reply is that the 
flow and ebb in our Mediterranean seas does not cause so much varia- 

PHYSICAL GEOGRAPHY 335 

don because in the Gulf of Genoa it does not vary at all, at Venice and 
in Africa only a little, and where it varies only a little it covers but little 
of the country. Leic. 9 r. 

Refutation of such as say that the shells were carried a distance of 
many days' journey from the sea by reason of the Deluge. 

I hold that the Deluge would not be able to carry up into the moun- 
tains objects native to the sea unless the sea had become so swollen as to 
form a flood so great that it even mounted above the height of these 
same places, and this process could not have occurred because it would 
have created a vacuum; and if you should say that the air would rush 
in there we have already concluded that what is heavy cannot be sup- 
ported on what is light wherefore we conclude of necessity that this 
Deluge was caused by rain water; and if this was the case all this 
water flowed into the sea and the sea does not flow up the mountains; 
and if it ran into the sea it pushed the shells along the shore into the 
sea and did not draw them to itself. And if you should say that be- 
cause the sea was raised by rain water it carried these shells to such a 
height, we have already stated that things heavier than water cannot 
float upon its surface but remain at the bottom and are not moved from 
there unless by pressure from the waves. And if you were to say that 
it was the waves which had carried them to these high places we have 
proved that the waves when of great depth move in an opposite di- 
rection at their base to their movement above, this being shown by the 
turbidity of the sea arising from the soil that has been washed away 
near its shores. 

An object lighter than water moves with its wave and it is left on the 
highest spot of the bank by the highest wave; an object heavier than 
water moves only when driven by its wave along the surface of its bed. 
And from these two conclusions which in their places will be fully 
proved we may conclude that the wave of the surface cannot carry 
shells because they are heavier than water; and consequently they will 
be driven by the lower wave when the wind comes from the land, be- 
cause when the wind comes from the land the wave at the bottom of 
the sea moves in the opposite direction to the course of the wind which 
is then prevailing; and this moreover will not cause the shells to be 
carried to the mountains, because the water at the bottom which moves 

336 PHYSICAL GEOGRAPHY 

in the opposite direction to the wind will be so much slower than the 
wave of the surface as it is deeper than the height of the wave. This 
is evident because if the wave of the surface is the height of one braccio 
and there are a hundred braccia of water below it then without doubt 
the lower wave will be a hundred times slower than the upper wave, as 
is shown in the seventh proposition. The upper wave will never turn 
back on its base with any great force unless the depth of the water that 
is below the wave is equal to that of the wave. 

The tiny wave which may be seen on the high seas travelling against 
the course of the wind will not pass over its base, that is it will not 
touch it but will dissolve at contact with the surface wave. I hold that 
such movement of water, changing from its surface to its base, re- 
sembles that which takes place on the surface between two banks, see- 
ing that if a third of the expanse of the river be moving towards the 
west, another third will move towards the east and the remainder to 
the west; and if there should be another similar part there that would 
return to the east. The lateral movements of rivers will become slower 
in proportion as they are farther removed from the first current. As 
regards the friction created by water inside other water and moving 
more swiftly, whether it divides immediately, that is whether the edges 
of this body of water are worn away or follow one after another, that 
is the swifter portion carrying the less swift with it, — I maintain that 
this is not the case, for if it carried with it more water than usual it 
would grow to such a size during its long course that it would be carry- 
ing with it all the water of the river. 

Why the oysters are very seldom found dead on the shores of the 
sea is because usually they live fastened to the rocks at the bottom of 
the sea and are incapable of movement except in the half which is 
sensitive and light. The other valve is fixed to the stone or if not fixed 
nature has caused them to grow larger and so to become so heavy that 
the small amount of undulation which takes place in the vast depths of 
the sea cannot easily dislodge them. But the valve that has the power 
of movement is very light and performs the same function for it as the 
lid does for a chest. And when the oyster feeds, its food walks into the 
house of its own accord, for it consists of certain animalculae which 
feed round the shells of the dead ones and which consequendy are 
found where there are a great many shells of dead oysters. If the 

PHYSICAL GEOGRAPHY 337 

Deluge had carried the shells lor distances ol three and tour hundred 
miles from the sea it would have brought them with the various diiTer- 
ent species mixed up, all heaped up together; but even at such dis- 
tances from the sea we see the oysters all together and also the shell-fish 
and the cuttle-fish and all the other shells which stand together in com- 
panies, found all together dead, and the single shells are found one at 
a distance from another as we see them every day on the sea shores. 

And we find the oysters together in very large families, among which 
some may be seen with their shells still joined together, which serves to 
indicate that they were left there by the sea and that they were still 
living when the straits of Gibraltar were cut through. 

In the mountains of Parma and Piacenza multitudes of shells and 
corals filled with worm-holes may be seen still adhering to the rocks, 
and when I was making the great horse at Milan a large sack of those 
which had been found in these parts was brought to my workshop by 
some peasants, and among them were many which were still in their 
original condition. 

Under the ground and down in the deep excavations of the stone- 
quarries timbers of worked beams are found which have already be- 
come black. They have been found during my time in the excavations 
made at Castel Fiorentino, and they were buried there before the sand 
deposited by the Arno in the sea which then flowed over the spot had 
been raised to such a height, and before the plains of the Casentino had 
been so much lowered by the removal of the earth which the Arno was 
continually washing away from them. 

In Candia, in Lombardy, near to Alessandria della Paglia, while 
some men were engaged in digging a well for Messer Gualtieri who 
has a house there, the skeleton of a very large ship was found at a 
depth of about ten braccia beneath the ground; and as the timber was 
black and in excellent condition, Messer Gualtieri thought fit to have 
the mouth of the well enlarged in such a way that the ends of the ship 
should be uncovered. 

The red stone of the mountains of Verona is found with shells all 
intermingled which have become part of this stone, and their mouths 
have become sealed up by the cement of which the stone has been 
formed, and portions of them have remained separated from the rest 
of the mass of stone which enclosed them, because the outer covering of 

338 PHYSICAL GEOGRAPHY 

the shell intervened and thus prevented them from uniting; and in 
other cases this cement has petrified the old broken outer covering. 

And if you should say that these shells have been and still constantly 
are being created in such places as these by the nature of the locality 
and through the potency of the heavens in those spots, such an opinion 
cannot exist in brains possessed of any extensive powers of reasoning 
because the years of their growth are numbered upon the outer cover- 
ings of their shells; and both small and large ones may be seen, and 
these would not have grown without feeding or feed without move- 
ment, and here they would not be able to move. Leic. 9 v. 

How the northern bases of certain Alps are not yet petrified; this is 
seen clearly where the rivers which cut through them flow towards the 
north, for these cut through the strata of the living rock in the moun- 
tain heights; and where they unite with the plains these strata are all of 
clay that serves to make pots, as is seen in the Val di Lamona where 
the river Lamona as it issues from the Apennines does these same 
things in its banks. 

How the rivers have all sawn through and divided the members of 
the great Alps one from another; and this is revealed by the arrange- 
ment of the stratified rocks, in which from the summit of the moun- 
tain down to the river one sees the strata on the one side of the river 
corresponding with those on the other. How the stratified rocks of the 
mountains are all in layers of mud deposited one above another by the 
floods of the rivers. How the different thicknesses of the strata of the 
rocks are created by the different floods of the rivers, that is the greater 
and the less floods. 

How between the various layers of the stone are still to be found the 
tracks of the worms which crawled about upon them when it was not 
yet dry. How all the marine clays still contain shells, and the shell is 
petrified together with the clay. Of the stupidity and ignorance of those 
who imagine that these creatures were carried to such places distant 
from the sea by the Deluge. 

How another set of ignoramuses maintain that nature or the heavens 
have created them in these places through celestial influences; as 
though in those places one did not find the bones of fishes which have 
taken a long time to grow; as though one could not count on the shells 

PHYSICAL GEOGRAPHY 

or cockles and snails the number of the months and years nl their lives, 
fust as one can on the horns of bulls and wethers and in the ramifica- 
tion of plants when they have never been cut in any part. And having 
shown by these signs that the length of their life is evident, it must 
needs be admitted that these animals could not live without the power 
of movement in order to seek their food, and we cannot see that they 
are equipped with any instrument for penetrating the earth or stone in 
which they find themselves enclosed. But how could one find in the 
shell of a large snail fragments and bits of many other sorts of shells of 
different kinds unless they had been thrown into it by the waves of the 
sea as it lay dead upon the shore like the other light things which the 
sea casts up on the land ? 

Why do we find so many fragments and whole shells between the 
different layers of the stone unless they had been upon the shore and 
had been covered over by earth newly thrown up by the sea which then 
became petrified? And if the above-mentioned Deluge had carried 
them to these places from the sea, you would find the shells at the edge 
of one layer of rock only, not at the edge of many where may be 
counted the winters of the years during which the sea multiplied the 
layers of sand and mud brought down by the neighbouring rivers, and 
spread them over its shores. And if you should wish to say that there 
must have been many deluges in order to produce these layers and the 
shells among them it would then become necessary for you to affirm 
that such a deluge took place every year. Further as regards the frag- 
ments of these shells, it must be presumed that in such a locality there 
was a sea beach, where the shells were all cast up broken and divided 
and never in pairs as they are found in the sea when alive, with two 
valves which form a covering the one to the other. And within the 
layers of the banks of rivers and of sea shores they are found broken; 
and on the edges of the rocks they are found infrequently and with the 
two valves together, like those which were left by the sea buried alive 
within the mud which afterwards dried up and in time became petri- 
fied. Leic. 10 r. 

And if you should say that it was the Deluge that carried these shells 
away from the sea tor hundreds of miles, this cannot have happened for 
the Deluge came about as the result of rains, because the rains natu- 

340 PHYSICAL GEOGRAPHY 

rally cause the rivers together with the objects carried by them to rush 
towards the sea and they do not draw up to the mountains the dead 
things on the sea shores. 

And if you should say that the Deluge then rose with its waters above 
the mountains, the movement of the sea in its journey against the 
course of the rivers would have been so slow that it would not have 
been able to carry things heavier than itself floating in it; or if some- 
how it had had them floating in it then as it subsided it would have 
left them strewn about in various places. But how are we to account for 
the fact of the corals being found every day round about Monferrato 
in Lombardy with worm-holes in them, sticking to the rocks which 
have been left bare by the currents of the rivers? And the said rocks 
are all covered with stocks and families of oysters, which as we know 
do not move but always remain fixed by one of their valves to the rock, 
having the other open in order to feed upon the animalculae that are 
swimming about the waters and which while hoping to find good pas- 
ture become the food of the above-mentioned shells. Is it not found 
that the sand that is mixed with the seaweed has become petrified when 
the seaweed which has divided it has become less? And of this the Po 
affords instances every day in the debris of its banks. 

At Alessandria della Paglia in Lombardy there is no other stone from 
which to make lime except such as is made up of an infinite number of 
things native to the sea; but it is now more than two hundred miles 
distant from the sea. 

In eighty-nine [the year 1489] there was an earthquake in the sea of 
Satalia near to Rhodes, and it opened the depths of the sea and into the 
opening that was made such a torrent of water was poured that for 
more than three hours the bed of the sea lay bare because of the water 
which had been lost from it, and then it closed up again to its former 
level. Whatever changes may occur in the weight of the earth the sur- 
face of the sphere of waters will never cease to be equidistant from the 
centre of the world. 

The bosom of the Mediterranean like a sea received the principal 
waters of Africa, Asia and Europe; for they were turned towards it and 
came with their waters to the base of the mountains which surrounded 
it and formed its banks. 

And the peaks of the Apennines stood up in this sea in the form of 

PHYSICAL (i EOG RA I'HY 341 

islands surrounded by salt water. Nor did Africa as yet behind its Adas 

mountains reveal the earth of its great plains naked to the sky some 
three thousand miles in extent; and on the shore of this sea stood 
Memphis; and above the plains of Italy where flocks of birds are flying 
to-day fishes were once moving in large shoals. Leic. 10 v. 

That there are springs which as a result of earthquakes or other un- 
foreseen causes suddenly burst forth and as suddenly fail. And this 
happened in a mountain in Savoy where certain woods sank in and left 
a very deep abyss; and at about four miles distance from there the 
ground opened on the slope of a mountain and threw out suddenly an 
immense flood of water, which swept through a whole valley of tilled 
fields vineyards and houses and did irreparable damage wherever it 
spread. 

That there are many springs which come to fail suddenly: and this 
happens through some subsidence in a cavern that is pent up within 
the body of the earth whereby the passage of the said springs is 
blocked and hindered. 

That there are many springs which spring up suddenly and are 
permanent; and this occurs when some river in its long course has 
worn away so much of the mountain that it bursts open springs of 
water which have a passage there; it may also occur as I said before 
when a cave has fallen in ruin and blocked up a spring, so that its 
water has been forced up to such a height in this cavern that it reaches 
the level of some fissure in the rock and so has made its escape, creat- 
ing a new river. 

That many springs of salt water are found at great distances from 
the sea; and this may have come about because these springs have 
passed through some mine of salt like that in Hungary where the salt 
is hewn out of immense quarries just as blocks of stone are. 

That within rocks surrounded by salt waters and within these salt 
waters themselves in the same way there rise in many places springs of 
fresh water. 

That there are in many places springs of water which rise for six 
hours and sink for six hours; and I have myself seen one above Lake 
Como called Fonte Pliniana which increases and decreases in this way 
to such an extent that when it is flowing it grinds two mills, and when 

342 PHYSICAL GEOGRAPHY 

it fails it falls so low that it is as though one were looking at the water 
in a deep well. Leic. n v. 

A tempest on the sea is much more violent near to the shore than on 
the high sea; and this is the case because the recoil of the waves is strik- 
ing the sea on the one side and the wind strikes it on the other, and this 
causes the wave to be higher and more topped with spray. Leic. 12 r. 

How the flow and ebb of the tide is not uniform, for on the coast of 
Genoa there is none; at Venice it makes a variation of two braccia; be- 
tween England and France of eighteen braccia. How the current that 
flows through the straits of Sicily is very powerful because through 
these there pass all the waters of the rivers which discharge themselves 
into the Adriatic. 

When the surface of the water consists of small shaded waves which 
form themselves into lines that meet in an angle, 1 the fact shows that 
the bed of the river is not far away, and it is also produced by the sand 
thrown off by the water as it passes through a confined space such as 
the arch of a bridge or the like. When the lines of its surface form a 
curved or crescent shaped figure this is a sign of its lack of depth, for 
it is caused by the sand carried by the greater current into the lesser, 
that is by the less sluggish to the more sluggish, since both of them have 
but little speed or depth. When the surface of the water shows itself as 
a straight line or just a little bent with tiny waves and these with but 
little sheen or brightness there is very little depth there; and this is 
caused by two currents one slower than the other which join together 
again below the island that divides them higher up; for these have 
caused the sand which each bore with it to settle, because it is deposited 
at the point of their junction, since at this spot their movement ended. 

Leic. 13 r. 

Why the bones of great fishes and oysters and corals and various 
other shells and sea-snail are found on the high tops of mountains that 
border on the sea, in the same way in which they are found in the 
depths of the sea? 

1 These words serve exactly to describe the treatment of the waves in Botticelli's 
'Birth of Venus'. 

PHYSICAL GEOGRAPHY J43 

How the rocks and promontories of the seas are being continually 
destroyed and worn away. 

How the Mediterranean seas will lay bare their depths to the air, 
and will only keep the channel of the greatest river that flows there 
which will run to the ocean and there discharge its waters together 
with those of all the rivers which are its tributaries. 

How the brightness of the atmosphere is caused by the water that 
is dissolved in it and that has formed itself into imperceptible particles 
which after taking the light of the sun from the opposite side give 
back the brightness that is visible in this atmosphere; and the blue 
that appears in it is caused by the darkness which is hidden behind 
this atmosphere. 

Why the Adige rises every seven years and falls every seven years, 
and is the cause of famine or abundance? 

Why following on great pestilences the rivers become deeper and 
run clear though previously they were wide and of but little depth 
and always turbid? Leio 20 r. 

The sea shuts itself in among the great valleys of the earth; and this 
earth serves as a cup for the sea; and the lips of the cup are the shores 
of the seas, and if these were taken away the sea would cover all the 
earth; but because every part of the earth that is uncovered is higher 
than the greatest height of the sea this sea cannot flow over it, but 
merely contents itself with covering that earth which serves as its bed. 
Many, however, in ignorance of this thing, have presumptuously writ- 
ten how the surface of the water of the sea is higher than the highest 
mountain that can be found; as regards which thing, although they 
see the bank higher than the water, they are extremely blind who say 
that it is a miracle for the water in the midst of the sea to be higher 
than its shore or than the promontories which jut out over the sea. But 
this fallacy arises from the fact that they imagine a straight line of 
indefinite length extended above the middle of the sea, which without 
doubt will be higher than the said shores, because the earth is a 
sphere and its surface forms a curve, and the farther it is removed 
from its middle the more it becomes remote from the said straight 
line; the fact of it becoming lower in this condition is that which has 
deceived them; and it is this reason which will be brought forward 

344 PHYSICAL GEOGRAPHY 

by the adversary. 'That part of the water will be higher which is more 
remote from the centre of the world'. 

Observe that here there is no place for the straight unending a b of 
the adversary, because b g exceeds the line e g by the whole part b n; 
and by this it is confirmed that the surface of the seas which are joined 
together are equally distant from the centre of the earth. 'The highest 
mountains are as far above the sea as the lowest depths of the sea arc 
below the air.' 

For a long time the water of the Mediterranean flowed through the 
Red Sea which is a hundred miles wide and fifteen hundred miles 
long, all full of reefs; and it has worn away the sides of Mount Sinai, 
which circumstance does not point to a flood from the Indian Ocean 
having struck upon these shores but to a great deluge of water which 
carried with it all the rivers which are very numerous round the Medi- 
terranean, and also the ebb of the sea. And afterwards Mount Calpe 
was cut through in the west, three thousand miles distant from this 
spot, and separated from Mount Abyla; and this cutting took place 
at the lowest spot in the wide plains which lie between Abyla and the 
ocean, in the low part at the foot of the mountain, helped by the 
hollowing out of some valley caused by some river which must have 
flowed there. Hercules came to open the sea in the west, and then the 
waters of the sea commenced to flow into the western ocean; and as a 
consequence of this great fall the Red Sea remained the higher, 
and therefore the waters have ceased to flow in that direction but have 
always ever since poured through the Straits of Spain [Gibraltar]. 

On the shores of the Mediterranean three hundred rivers are found 
discharging their waters and there are some forty thousand two hun- 
dred harbours, and this sea is three thousand miles in length. Many 
times the swollen waters of the sea have been heaped up by its reflux, 
by the western gales, the flooding of the Nile and of the rivers which 
flow into the Black Sea. So the seas came to be so much raised that 
they have flowed over many countries causing immense floods; and 
these floods occur at the time when the sun melts the snow on the 
high mountains of Ethiopia which rise into the cold regions of the 
air; even so is it as the sun approaches near to the mountains of Sar- 
matia in Asia and to those in Europe; so that the accumulations 
occasioned by these three above-mentioned things are and have been 

PHYSICAL GEOGRAPHY 345 

the cause of the greatest Hoods, namely the ebb oi the sea, the western 

wind and the melting of the snows. And all things have been over- 
whelmed in swirling Hood in Syria, Samaria, Judaea between Sinai 
and Lebanon, and in the rest of Syria between Lebanon and Mount 
Taurus, and in Cilicia within the mountains of Armenia, and in 
Pamphylia and in Lycia within the Celenian mountains, and in 
Egypt as far as Mount Atlas. The Persian Gulf which was once a vast 
lake of the Tigris and had its outlet into the Indian Ocean, has now 
worn away the mountain which served it as a bank, and become the 
same level as the Indian Ocean. And if the Mediterranean had con- 
tinued to find an outlet through the Gulf of Arabia it would have 
produced the same result, that is it would have caused its level to 
become the same as that of the Indian Ocean. 
[ With dra wing\ 

In this one has to imagine the earth sawn through the centre; and it 
will show the depth of the sea and of the earth; [and how] the 
springs start from the bottoms of the seas, and wind their way 
through the earth, and raise themselves to the summits of the moun- 
tains, and flow back again through the rivers, and return to the sea. 

Since things are far more ancient than letters, it is not to be won- 
dered at if in our days there exists no record of how the aforesaid seas 
extended over so many countries; and if moreover such record ever 
existed, the wars, the conflagrations, the changes in speech and habits, 
the deluges of the waters, have destroyed every vestige of the past. But 
sufficient for us is the testimony of things produced in the salt waters 
and now found again in the high mountains, sometimes at a distance 
from the seas. Leic. 31 r. 

That part of the flow and ebb of the sea will be of greater variety 
from its greatest height to its lowest depth which is nearest to its 
cause. 

There is great variation between the ebb and flow of the sea in the 
vicinity of those places at which the springs of the waters depart from 
the depths of the seas in order to supply a perpetual stream of water 
to the rivers which afterwards descend from the high mountains. 

These springs are of two natures, of which one is of those that are 

346 PHYSICAL GEOGRAPHY 

continually discharging themselves in the rivers; and there are others 
that pour themselves into the sea, and rise fresh above the other salt 
waters: which thing proceeds from the fact of them being born from 
the lakes that lie open to the air, which are higher than the waters of 
the sea, otherwise this rising would not take place. And yet one might 
say that just as the springs of the mountains are poured to their feet, 
so such springs might also be poured beneath the sea. 

There is a spring in Sicily which as it rises at certain seasons of the 
year throws out chestnut leaves in large quantities. Since however 
chestnut trees do not grow in Sicily this spring must have come orig- 
inally from some underground lake in Italy and then passed beneath 
the sea and afterward found outlet in Sicily. 1 

In the Bosphorus the Black Sea always flows into the Aegean, never 
the Aegean into it. This is due to the fact that the Caspian Sea, five 
hundred miles to the east, together with the rivers that flow into it, is 
always discharging itself through subterranean channels into the Black 
Sea; and the Don and also the Danube do the same; so that as a con- 
sequence the waters of the Black Sea are always higher than those of 
the Aegean, and it follows that the higher always descend into the 
lower and never the lower into the higher. 

Some say that the waters which rise in the summits of the high 
mountains, are part of the water of the sea which is higher than the 
summits of the highest mountains that exist; which serves them to 
prove that the surface of the sea is lower than any part of the earth 
that stands above the waters, or that any part of the surface of a river 
which flows into this sea. 

Others say that the waters which flow above the high summits of 
the mountains are descended from the higher mountains of the 
world which are covered with snow that melts during the summer. 
But this opinion is shown to be incorrect, for if it were the case that 
the melting snows of summer entering into subterranean caverns and 
through the springs in the ground had sent the water in the tops of 
the mountains lower than the mouths of the springs, there would be 

1 Richter points out that the chestnut is a common tree in Sicily and suggests that 
Leonardo may have written 'Cicilia' in mistake for Cilicia. 

PHYSICAL GEOGRAPHY 347 

more water in these springs in summer than in winter, but experience 
shows that the opposite is the case. 

All the outlets of the waters which proceed from the mountain to 
the sea carry stones from the mountains with them to the sea; and by 
the backwash of the ocean surges against their mountains these stones 
were thrown back towards the mountain; and as the waters moved 
towards the sea and returned from it the stones turned with them, and 
as they were rolled back their corners struck together, and such parts 
of them as offered least resistance to the blow were worn away and 
make stones without angles of a round shape, such as are to be seen 
on the shores of Elba. And those remain bigger which are carried the 
least distance from their native spot, and in like manner the stone be- 
comes smaller which is transported farther away from the aforesaid 
spot, for in the course of its progress it becomes changed to fine 
shingle and then to sand and finally to mud. After the sea had receded 
from the aforesaid mountains the salt deposit which it left behind 
with the other moisture from the earth formed a compound with the 
shingle and sand so that the shingle became changed to rock and the 
sand to tufa. 

And of this we may see an example in the Adda where it emerges 
from the mountains of Como, and in the Ticino the Adige the Oglio 
and the Adriano from the Austrian Alps; and in the same way with 
the Arno from Monte Albano round about Monte Lupo and Capraia, 
where the largest rocks are all formed of solidified shingle of different 
varieties of stone and of different colours. 

That thing which is lighter will be carried farther by the rivers from 
the place whence its waters snatched it away; and so that which is 
heavier will be removed a less distance from the place at which it was 
separated. That percussion of the water carries away more of the bank 
of rivers which strikes this bank at more equal angles; and so con- 
versely it will carry away less when the angles are more unequal. 

Leic. 31 v. 

There are as many differences in the resistance made by water be- 
neath that which is supported by it as there are differences in its heat 
or cold. 

Given two rivers of equal volume of water at their entrances, their 

348 PHYSICAL GEOGRAPHY 

exits will be equal; that is, given an equal volume of water in an equal 
time, even though the rivers may vary in length, breadth, slant and 
depth and the one be twisted and the other straight; or though both 
be twisted but the shapes of their curves are unlike; or one be of uni- 
form breadth and the other of varying breadth; and if both vary their 
variation may be different ; one may be of uniform depth and the 
other of varying depth; and should both depths vary in themselves 
their variation may not have any kind of likeness; and the whole of 
one may be uniformly swift and the other uniformly slow, or the 
slowness and swiftness of one may be mixed, that is where it runs and 
where it lingers, where the waters fall perpendicularly and where they 
rise in a swirling flood; and the fact that there exist in these two rivers 
infinite varieties of currents in breadth, length, slant and depth will not 
therefore prevent the equal entrance of the one from being equal to its 
exit, and the equal entrances of the one and the other from being equal 
in their exits. 

If the Mediterranean Sea departs from its site it raises the sphere of 
the water and occupies new valleys, and consequently the centre of 
gravity of this increase will be round the antipodes; and so on that side 
the weight grows, and on this there is lacking the whole amount of 
the weight of the water that has departed from there; and although 
this position may be filled up by that earth which was carried by the 
rivers into this Mediterranean, the centre of its gravity will be oppo- 
site to that of the sphere which has been increased in the antipodes; 
and so on this side the weight is not increased by the earth which has 
been removed as a substitute for the sea which has been expelled, be- 
cause this earth remains in our hemisphere, that is, the centre of its 
gravity, but it is nevertheless true that the whole weight of the water 
is here diminished. Therefore the centre of the world will become 
nearer to our antipodes, lightening itself here of the weight of the 
water which has departed; and the summits of the mountains will 
raise themselves more from this centre: until such a point that the 
rivers which accompany the Nile after much rambling about through 
the great plain into which the Mediterranean is divided will carry 
through the straits of Gibraltar all the part of the soil that makes it 
turbid; and in the course of time they will place as much soil in the 
ocean bevond the straits of Gibraltar as is found between Libya and 

PHYSICAL G EOGRAPHY 349 

the sea, and between the Alps and the said sea; and so again the centre 

of the world will become nearer die centre of the weight increased to 
the ocean, and the parts lightened will become more remote from this 
eentre. So then it is concluded that the more the soil is removed from 
US the more it lightens our regions; as a consequence the more it is 
removed from the centre of the earth the more the waters consume it 
and the more again it becomes light; and so it will continue until 
all the earth laid bare is carried to the sea by the Nile or by the rivers 
that are poured into it. 

And so the earth that is found in the rivers that now pour them- 
selves into the Mediterranean will be carried by the Nile together 
with the turbid water that remains in it to the ocean. 

So then the sea will return to cover the places where were formerly 
the roots and bases of the mountains, and it will cover the earth. 

It is not denied that the Nile is always turbid as it enters the Egyp- 
tian sea, and that this turbid condition is due to the soil which this 
river carries away continually from the places through which it passes, 
and this soil never returns back nor does the sea receive it except just 
to cast it back upon its shores; behold the ocean of sand beyond 
Mount Atlas where it was once covered with salt water. 

The water that is found in the highest mountains is not there be- 
cause it has been drawn there by the heat of the sun for but little of 
this heat passes downwards, as is seen below La Vernia, where the 
power of the sun is not sufficient to melt the ice during the greatest 
heat of summer, but it remains there in the hollows in which it has 
been lying since the winter. And on the northern slopes of the Alps, 
where the sun does not strike, the ice never melts, because the heat of 
the sun cannot penetrate the small thickness of the mountains; still 
less therefore will the vast space that lies between the summits of the 
great mountains and the depths of the watery sphere be penetrated by 
this heat of the sun which would have to pass beneath the base of this 
mountain. If you should say that the earth's action is like that of a 
sponge which when part of it is placed in water sucks up the water so 
that it passes up to the top of the sponge, the answer is that even if 
the water itself rises to the top of the sponge, it cannot then pour 
away any part of itself down from this top, unless it is squeezed by 

350 PHYSICAL GEOGRAPHY 

something else, whereas with the summits of the mountains one sees ir 
is just the opposite, for there the water always flows away of its own 
accord without being squeezed by anything. 

Perhaps you will say that water can only rise the same distance as it 
descends; and that the surface of the sea is higher than the summits 
of the highest mountains. The answer to this is that the exact opposite 
is the case, for the lowest part visible to the sky is the surface of the 
sea, since water does not move of itself unless to descend, and so de- 
scends when it moves; as therefore the rivers which stretch from the 
summits of the mountains to the sea are everywhere in movement 
they are therefore everywhere descending, and when they come to the 
sea they stop and end their movement; for which reason one must con- 
clude that they are stationary in the lowest reaches of the river. But 
if you should say that the farther the sea is away from the shore the 
more it rises up and so it comes to equal the height of the high moun- 
tains; it is shown here that a thing is higher which is farther removed 
from the centre of the earth, and if the element of water is spherical 
the definition of spherical bodies is those in which every part of the 
surface is equidistant from the centre. So therefore the shore of the sea 
is as high as its centre, and whatever may be discerned from the shore 
is higher than any part of the sea; and the distance that there is from 
the summits of the high mountains to the centre of the earth is greater 
than the distance from this centre to the sea shore: this then is our 
conclusion. 

And if you should say as has been said that the sun sucks up and 
draws the waters from the roots of the mountains to their summits, 
then as the heat draws the moisture to itself the heat which is more 
powerful would draw to itself a greater amount of water than the less 
powerful. In summer therefore during the fiery heats the springs of 
the waters would have to rise higher into the summits of the moun- 
tains than they do in winter; but we see it is the contrary seeing that 
in summer the rivers lack a great part of their waters. Eeic. 32 v. 

OF THE ORIGIN OF RIVERS 

The body of the earth like the bodies of animals is interwoven with 
a network of veins which are all joined together, and are formed for 

PHYSICAL GEOGRAPHY 351 

:he nutrition and vivifying of this earth and of its creatures; and they 
originate in the depths of the sea, and there after many revolutions 
they have to return through the rivers formed by the high burstings 
of these veins. And if you should wish to say that rains in winter or 
the melting of the snow in summer were the cause of the origin of 
the rivers, one may offer as an instance the rivers which originate in 
the torrid regions of Africa in which it does not rain still less does it 
snow, because the excessive heat always dissolves into air all the clouds 
which are driven there by the winds. And if you should say that these 
rivers which become big in July and August are from the snow which 
melts in May and June as the sun approaches nearer to the snowfields 
of the mountains of Scythia, and that the snow thus melted collects 
in certain valleys and forms lakes, into which it enters by springs and 
underground caverns, afterwards emerging to form the source of the 
Nile, this is incorrect because Scythia lies below the source of the Nile, 
and Scythia moreover is only four hundred miles from the Black Sea 
whereas the source of the Nile is a distance of three thousand miles 
from the Egyptian sea into which it pours its water. Leic. 33 v. 

In the western parts near to Flanders the sea rises and falls about 
twenty braccia every six hours; and twenty-two when the moon is 
favourable; but twenty braccia is its usual variation and this as is 
clearly seen is not caused by the moon. This variation in the rising 
and falling of the sea every six hours may occur through the swelling 
up of the waters which are poured into the Mediterranean by the 
number of the rivers from Africa Asia and Europe that pour their 
waters into this sea; and this gives back to the ocean through the 
straits of Gibraltar between the promontories Abyla and Calpe the 
waters given to it by these rivers. 

This ocean as it extends between the island of England and other 
islands farther north, comes to swell up and form a bore at the mouths 
of certain gulfs, which, being as it were seas, with the surface separated 
from that of the central body of the earth, have acquired weight, and 
this, as it exceeds the force of the incoming waters that occasioned it, 
causes this water to take again an impetus contrary to that of its ap- 
proach, and so creates an impetus contrary to that which the waters 
have given the straits, and especially against the straits of Gibraltar, 
which for as long as this is going on remain in swirling flood, holding 

352 PHYSICAL GEOGRAPHY 

hack all the water recently given them at that time by the aforesaid 
rivers; and this would seem to be one of the reasons which may be 
assigned for this ebb and flow; as is proved in the twenty-first of the 
fourth of my book on Theory. This would occur when the water that 
formed the springs of rivers was caused by rain or melting snow. But 
if these springs had their origin in the depths of the sea this reason 
would not exist, for at their beginning the sea would give them as 
much water as the rivers gave the sea, namely what they received 
from the ends of their springs; and so for this cause the sea would 
not increase or grow less. 

The stratified rocks are created in the vast depths of the seas because 
the mud which the storms detach from the sea coasts is carried out to 
the deep sea by the recoil of the waves; and after these storms it is 
deposited upon the bottom of the sea, and as no storm can penetrate 
the sea on account of the great distance that it is below the surface it 
lies there motionless and becomes petrified; and sometimes it remains 
in the form of white clay which serves for making pots; and thus with 
blocks set at different angles it is made up of layers of as many differ- 
ent thicknesses as are the differences in the storms whether greater 
or less. Leic. 35 r. 

WHETHER THE EARTH IS LESS THAN THE WATER 

Some assert as a fact that the earth which is not covered by the 
waters is much less than that which is covered by them; but since the 
size of the diameter of the earth is seven thousand miles, it may be 
concluded that as the water is almost universally of but little depth its 
weight bears no comparison to that of the earth. The answer to these 
is that the water which is poured into the atmosphere which becomes 
united as it rises to the cold region of the atmosphere is very heavy 
in weight and falls in great deluges and floods. And how do we know 
whether the earth has enormous caverns with reservoirs of water? 

And the innumerable springs which are fed by as many streams of 
water, as are seen in the formation of the rivers? Take as an instance 
the Caspian Sea which is very great. 

PHYSICAL GEOGRAPHY 353 

Always the centre of the sphere of the water, but not of its weight, 
because it is DOt of equal thickness spread over the earth, will he con- 
centric with the centre of the world; and it is the same as regards the 
centre of the gravity of the earth and of the waters joined together, 
but not of its gravity nor of its magnitude; and if the earth of itselt 
were spherical and without water within itself, then the water would 
clothe it with uniform size and weight; and so the centre of the world 
would remain centre of the sphere and magnitude of the water and 
of its weight; and so it would remain centre of the sphere and magni- 
tude of the earth, and centre of its gravity; consequently as the earth is 
mixed and full of the ramifications of the waters within itself, is in 
some parts spread out in some compact, in some soil, in some rock, 
this earth has not in itself a centre of sphericity or a centre of gravity, 
and this especially through it having water and earth above the sphere 
of the water, which give weight to it as though it was the weight of 
the earth. 

Consequently by this one concludes that the gravity of the earth and 
the water joined and mingled together have usually their centre con- 
centric with the centre of the world, which centre is also the centre of 
the spherical surface of the water, and not of its weight, as I have said 
above; and this surface of the sphere of the water is broken and di- 
vided by the earth which borders on the air. 

If the earth were entirely submerged by the water, even though it 
was of varied and irregular shape it would have the centre of its 
natural gravity concentric with the centre of the world and of the 
surface of the sphere of water, but not with the centre of its natural or 
even of its accidental gravity. 

That earth which is not covered by the waters will be much heavier 
than that which is beneath this water. 

The centres of the heavy bodies are three and they are differently 
situated, seeing that sometimes they are joined together; and here 
accidental gravity dies; sometimes there are two together and the third 
is separated from them; and here accidental gravity arises; and some- 
times they are placed together in three different positions, the one 
from the other : and the first is the centre of the magnitude, the second 
is the centre of its natural gravity, and the third the centre of the 
accidental gravity. 

354 PHYSICAL GEOGRAPHY 

The centre of the magnitude is that which is separated equally from 
the opposite extremities of the body that encloses it whether it be 
uniform or not; and it is sufficient that it is situated at an equal dis- 
tance from the opposite extremities of a staff, as of a cloth of any 
material. And these are joined together in a body of perfect sphericity 
and uniform substance and density, because here there are only two 
and they are concentric. 

Necessity makes the machine of the earth empty of earth and full 
of water, after the fashion of a vessel filled with water: 

This is confirmed by the tenfold proportion which the four elements 
have between them, which is seen of the air with the earth of which 
the proportion is a hundredfold, because the thickness of the air has 
been measured between the comet which is in the uppermost part of 
the air and with the surface of the sphere of the water which is in 
the lowest part of the sphere of the air. Now the water may be said 
to have as much earth uncovered which projects above the surface of 
the sphere of the water, as that which is lacking from the surface of 
the water towards the centre of the world, that is, I consider that the 
highest mountain that there is in the earth is as far above the surface 
of the sphere of the water as the greatest depth of the sea is below this 
surface of the sea. It follows that if one were to fill up the part want- 
ing in the sea with the excess of the earth, that this earth would re- 
main spherical and entirely covered by the sphere of the water. But, so 
far as one can discern, this sphere of water, or you may say element, 
would not be ten times as great as the sphere of the earth, but far from 
being ten times it would not attain to the relation of equality, because 
one sees clearly that the sphere of the water would not rise a mile 
above the sphere of the water, that is it would not raise itself to the 
altitude of the highest mountain; which thing however would take 
place when all the earth uncovered was everywhere as high as this 
highest mountain. 

Therefore it is concluded that the remainder of this water stays in 
the body and springs of the earth, in which it may have fallen over a 
wide area, and lightened the spot from whence it separated itself, as is 
represented opposite in B. 

In two ways the gravity of the earth can have its centre concentric 
with the centre of the world, that is if it is either altogether submerged 

PHYSICAL GEOGRAPHY 355 

by the waters or has its opposite side out of the waters of equal 
weight. 

The centre of the gravity of the water and of the earth might he- 
concentric with the centre of the world if the earth were perfectly 
spherical. The centre of the world would then be the centre of the 
sphere of the earth, as of the sphere of the water. But it would not 
produce land animals. Leic. 35 v. 

OF THE EARTH IN ITSELF 

The fact of the summits of the mountains projecting so far above the 
watery sphere may be due to the fact that a very large space of the 
earth which was filled with water, that is the immense cavern, must 
have fallen in a considerable distance from its vault towards the centre 
of the world, finding itself pierced by the course of the springs, which 
continually wear away the spot through which they pass, having in 
them some of the air above; because water has no weight unless it 
sends a wave out of its level through the air, and it is this wave alone 
that has weight and falls and wears away the base. Now this great 
mass has the power of falling, being the centre of the world within 
the water: it balances itself with equal opposing weights round the 
centre of the world, and lightens the earth from which it is divided; 
and it removed itself immediately from the centre of the world and 
rose to the height, for so one sees the layers of the rocks, formed by 
the changes which the water has undergone, at the summits of the 
high mountains. 

Subsidence of lands, as in the Dead Sea in Syria, to wit Sodom and 
Gomorrah. 

It must needs be that the water is more than the land; and the part 
uncovered by the sea does not reveal it; it must needs be therefore that 
there is a great mass of water within the earth, in addition to that 
which is diffused through the lower parts of the atmosphere and runs 
through the rivers and springs. 

I say that it is not necessary that the centre of the world be situated 
more in the earth than in the water, because the gravity of the earth 
and of the water, joined together in any manner whatever, rests with 

356 PHYSICAL GEOGRAPHY 

weights of gravity situated oppositely around the centre of the world; 
and the earth does not expect to have parts of itself equally distant 
from this centre, but weights equally heavy placed opposite; and in 
this case the water being mingled with various ramifications of springs 
together with the earth, cannot give of itself weights equally distant 
from this centre, but will have a surface equidistant from this centre. 

Now if it is as has been said, it is possible, the centre of the world 
being situated in the water, that on some occasion, through the con- 
stant friction that the water has through the springs through which 
it passes, it may have so widened these springs that the part of the 
earth which is interposed between these springs, exhausting the tenacity 
of the remainder, [brings it about] that the gravity, which it has ac- 
quired through being above the water, has detached itself from this 
remainder and has fallen towards the centre and made this concentric 
with the centre of its gravity. And through this the remainder of the 
earth having made itself lighter by that part from whence the said 
gravity fell, will of necessity remove itself from the centre of the 
world, and the earth and the mountains will emerge out of the sphere 
of the water lightened by this part, and will also make itself lighter by 
the weight of the water which rested upon it, and will come so much 
the more to raise itself towards the sky. And the sphere of the water 
in this case does not change its position, because its water fills up the 
place from which the gravity of that part of the earth that fell divided 
itself; and thus the sea remains in itself without change of height. 
And this may also be the reason why the marine shells and oysters 
that are seen in the high mountains, which have formerly been beneath 
the salt waters, are now found at so great a height, together with the 
stratified rocks, once formed of layers of mud carried by the rivers in 
the lakes swamps and seas; and in this process there is nothing that is 
contrary to reason. 

Given a perfectly smooth surface the water will not rest upon it: 
given a spherical surface the water will instantly rest there: which 
sphericity will be the sphere of the water. 

The strata or layers of stone do not continue to any great distance 
underneath the roots of the mountains because they are made of earth 
that is used for making vessels and is full of shells; and also these go 
only a short distance below because one finds the ordinary earth there, 

PHYSICAL GEOGRAPHY 357 

as is seen in the rivers whieh flow through the Marches and the Ro- 
magna, after they have issued from the Apennines. 

You have now to prove how the shells are not produced except in 
salt waters, and that this is the case with almost all kinds; and how 
the shells of Lomhardy are found at four levels. And so it is with all 
which are made at difTerent periods of time; and these are found in all 
the valleys that open out into the seas. Leic. 36 r.