997.

The element of fire acts upon a wave of air in the same way as the air does on water, or as water does on a mass of sand —­that is earth; and their motions are in the same proportions as those of the motors acting upon them.

998.

OF MOTION.

I ask whether the true motion of the clouds can be known by the motion of their shadows; and in like manner of the motion of the sun.

999.

To know better the direction of the winds. [Footnote:  In connection with this text I may here mention a hygrometer, drawn and probably invented by Leonardo.  A facsimile of this is given in Vol.  I, p. 297 with the note:  ’Modi di pesare l’arie eddi sapere quando s’a arrompere il tepo’ (Mode of weighing the air and of knowing when the weather will change); by the sponge "Spugnea" is written.]

The globe an organism.

1000.

Nothing originates in a spot where there is no sentient, vegetable and rational life; feathers grow upon birds and are changed every year; hairs grow upon animals and are changed every year, excepting some parts, like the hairs of the beard in lions, cats and their like.  The grass grows in the fields, and the leaves on the trees, and every year they are, in great part, renewed.  So that we might say that the earth has a spirit of growth; that its flesh is the soil, its bones the arrangement and connection of the rocks of which the mountains are composed, its cartilage the tufa, and its blood the springs of water.  The pool of blood which lies round the heart is the ocean, and its breathing, and the increase and decrease of the blood in the pulses, is represented in the earth by the flow and ebb of the sea; and the heat of the spirit of the world is the fire which pervades the earth, and the seat of the vegetative soul is in the fires, which in many parts of the earth find vent in baths and mines of sulphur, and in volcanoes, as at Mount Aetna in Sicily, and in many other places.

[Footnote:  Compare No. 929.]

XVII.

Topographical Notes.

A large part of the texts published in this section might perhaps have found their proper place in connection with the foregoing chapters on Physical Geography.  But these observations on Physical Geography, of whatever kind they may be, as soon as they are localised acquire a special interest and importance and particularly as bearing on the question whether Leonardo himself made the observations recorded at the places mentioned or merely noted the statements from hearsay.  In a few instances he himself tells us that he writes at second hand.  In some cases again, although the style and expressions used make it seem highly probable that he has derived his information from others—­ though, as it seems to me, these cases are not very numerous—­we find, on the other hand, among these topographical notes a great number of observations, about which it is extremely