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the implacable logician, "confess at least that they must have been left on the tops of the highest mountains, or in lakes at their bases, such as those of Como, Fiesole, Perugia, and the Lago Maggiore."
It is possible that Leonardo was first started on his geological researches by a passage in Boccaccio, in the story of Filocopo. Struck with the quantity of fossil shells in certain regions, the illustrious story-teller does not hesitate to look upon their presence as a sign that the ocean had once covered the continent.1 Another floating idea which Leonardo had the wit to appropriate!
Leonardo anticipated Cuvier in showing that the level of the sea's bottom is continually rising, sometimes suddenly and rapidly, sometimes by slow accumulations of all kinds of " debris." Mountains, according to him, are both made and destroyed by rivers. Their summits may have been the beds of rivers or of seas; but these, driven to retire by the slow corrosion of the mountain bases, have had to form other beds. Here is his profession of faith: "That the northern bases of some Alps are not yet petrified: and this is plainly to be seen where the rivers, which cut through them, flow to the north; where they cut through the strata in the living stone in the higher parts of the mountains, and where they join the plains, these strata are all of potter's clay, as is to be seen in the valley of Lamona, where the river Lamona, as it issues from the Apennines, demonstrates these things on its banks.— That the rivers have all cut and divided the mountains of the great Alps one from the other: this is visible in the order of the stratified rocks, because from the summits of the banks, down to the river, the correspondence of the strata in the rocks is visible on either side of the river.—That the stratified stones of the mountains are all layers of clay, deposited one above the other by the various floods of the rivers.—That the different size of the strata is caused by the difference in the floods: that is to say, greater or lesser floods." 1
1 See D'Archiac, Geologic et Palcontologic, p. 22, Paris, 1866. A contemporary of Leonardo, Alessandro degli Alessandri (1460-1523), thought he saw in the presence of petrified shells on the mountains of Calabria, a proof that the sea had once covered their summits, either by rising from its bed or through a change in the axis of the earth's rotation. Finally, Frascator set himself to show that the fossil shells found, about 1517, in the foundations of the citadel at Verona, could not have been left by Noah's Deluge, and that it was absurd to ascribe them to the plastic forces of nature or to Aristotle's equivocal generation; in short, ■ that the animals to which they belonged had lived on the spot, in water which had since betaken itself elsewhere.
Alluding elsewhere to a contemporary landslip (that, according to Dr. Richter, which took place above Bellinzona in 1515), Da Vinci says that, in his own times, "a mountain fell seven miles across a valley and closed it up, and also made a lake. And thus most
mountain lakes have been made, as the Lago di Garda, the lakes of Como and Lugano, and the Lago Maggiore." 2
It is not impossible that Leonardo explored the Piedmontese slopes of the Alps, and especially the Marquisate of Saluzzo; but his favourite regions were those about the Lake of Como. Starting from Lecco, he used to make his way into the Brienza mountains. It has, however, been ascertained that his geographical information about these neighbourhoods is not always quite exact. Thus he asserts that the four chief rivers which irrigate Europe—the Rhine, the Rhone, the Danube, and the Po—all have their origin at the foot of Monte Boso (Monte Rosa).3 Any modern schoolboy could demonstrate the absurdity of this assertion.
The low land behind the Atlas, the bed of the famous "mare internum," did not escape Leonardo's attention. "It is not denied that the Nile is constantly muddy in entering the Egyptian Sea, and that its turbidity is caused by soil that this river is continually bringing from the places it passes; which soil never returns in the sea which receives it, unless it throws it on its shores. Take, for instance, the sandy desert beyond Mount Atlas, formerly covered with salt water." 1
1 Richter, vol. ii. p. 205-206.
2 Richter, no. 1092.—Nowadays it is generally admitted that the formation of mountains is due to inequalities in the contraction of the earth's crust as it cooled, modified also by the pressure of the seas and by the flattening at the poles. I owe these explanations to the courtesy and erudition of Prince Roland Bonaparte.
3 Uzielli, Leonardo da Vinci e le Alpi, p. 18.
Leonardo's geographical studies come properly under the head of geology, for his interest was entirely given to physical geography. Logically enough, the other branches of the science were profoundly indifferent to him, like everything else that concerned history and politics.
Cartography must have reached a high point in Italy if we may judge from the maps of Leonardo, especially by that of Tuscany, in which the natural features, oreographic and hydrographic, of that province, are laid down with astonishing accuracy. He shows us Arezzo isolated in its marshes, Siena perched on its height, between Arbia, Chienna and Ciecina2; Chiusi dominates a lake, large as an inland sea, which seems to communicate with Lake Trasimene. Like those of the principal towns, the names of rivers are written in small capitals followed by the letters Yl. The names of minor towns are inserted in small letters.
A mistake has been made in associating Leonardo with the discovery of America. Following Ximenes, Grothe gravely alludes to a letter written by Leonardo in 1473, to Christopher Columbus, in which
1 Richter, vol. ii. p. 265.
2 Richter, pi. cxiii.
he discusses the possibility of reaching the East Indies by his, the explorer's, projected route !1
Even in the work of Uzielli we are told that we owe to Leonardo the oldest map extant bearing the name of America.- On this subject M. Henri Harrisse, the learned Americanist, writes to me as follows: "Among the papers of Leonardo now in England have been found the sections of a rude and elementary globe. These sections bear the name of America, and their configurations point to about the year 1515. Starting from this discovery, Mr. Mayor contributed a paper to Archccologia in which he contended that Leonardo himself was the author of the sections, an opinion now entirely abandoned. In any case, there are at least eight older maps of America, that of Juan de la Cosa, the pilot of Columbus, dated 1500; that of Alberto Cantino, made in 1502; that of Nicolay da Canerio, made in 1503; two maps published by Kunstmann in 1504, &c, &c."
With all these more abstract studies, Leonardo mingled practical applications and inventions, often of the humblest kind: vehicles, locks for canals, reduction-compasses with movable centres, instruments and machines of many kinds for drawing wire, twisting ropes, &c.
Leonardo, unlike most of his successors, laid down principles at the same time as he contrived applications; occasionally he even had the felicity of seeing his contrivances practically at work. He thus united in his own person three individuals, the theorist, the mechanical inventor, and the engineer, who are almost invariably distinct as M. Berthelot has so well explained in his work on Denis Papin. His drawings are enough to show that he was no mere theorist, but that he set his own fingers to the work, making machines and testing their efficiency for himself.
At the beginning of the seventeenth century the people ol Milan were still using a number of machines invented by Leonardo. They cut and polished rock crystal, marble, and iron witli his contrivances; they minced meat for sausages, and called in hydraulic power to supplement their own, with machines he had invented.
1 Leonardo da Vinci ah Ingenieur und Philosoph, p. 20.
2 Ricerche, 1st edition, vol. i. p. 15; vol. ii. p. 322-323.