PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 6G3 



its own heat a few feet lielow the surface. We see, then, at high 

 mountains, even under the equator, which, by their elevation, 

 are more distant from the common source of heat of the earth, 

 and have their interior so cooled down by radiation into space, 

 from their exposed situation, that the full sunshine can never melt 

 the snow on their summits, notwithstanding we know that the sun- 

 beam there has more heating power than below, not being 

 obstructed by the air, a fact sufficiently proved by Pouillet. 



We see, then, that all animal and vegetable life on earth has its 

 origin as well in the temperature of the earth itself, as in the heat 

 communicated by the sunbeam; that it cannot spare the one nor 

 the other, and only planets can possibly be provided with plants 

 and animals during a limited period in their career when those 

 two conditions agree. 



You all know that geology proves that the earth had, in the 

 beginning of its organized period, a much higher temperature; 

 that palm-trees and mammoths flourished around the poles Avhen 

 the tropics were unfit for organic life, and an impassal)]e barrier 

 between the two hemispheres. Some philosophers have attempted 

 to explain this former existence of tropical products in high lati- 

 tudes by the supposition of a shifting of the poles of the earth. 

 This idea proceeds from ignorance of the laws of motion, as I will 

 prove now with a few experiments. 



(Here the Doctor demonstrated practically by experiments w'ith 

 a beautiful rotation apparatus, that all bodies tend to rotate around 

 their shortest axis, and that this tendency is strong enough to over- 

 come a considerable amount of gravitation. Spheroidal bodies, 

 rings, and chains, when rotated around a longer axis, would shift 

 this axis till they rotated around the shortest, and an imitation of 

 Saturn and its rings, by rotating it rapidly, was made to lift itself 

 up against gravitation.) 



B}^ the contraction of the bulk of the earth, its rotary motion 

 did accelerate; its crust, when once surrounding it as a w^hole shell 

 became rimpled, and the principal mountain ridges did appeal' by 

 lateral pressure. By contimied contraction those rido-es, once 

 formed, rose higher and higher, and the depression deeper, lono- 

 before any ocean was precipitated on its surface. After atmos- 

 pheric and aquatic influences had acted for some thousands of years 

 on the elevated rocks, crumbling them, dissolving many substances 

 by the high temperature and pressure then prevailing in a boiling 

 ocean under an enormous atmospheric pressure, they were precipi- 



