Il8 LAMARCK, HIS LIFE AND WORK 



in the mass of the terrestrial radii, has necessarily 

 caused the earth's centre of gravity to vary, as also 

 its two poles.* Moreover, since it appears that this 

 variation, very irregular as it is, not being subjected 

 to any limits, it is very probable that each point of 

 the surface of the planet we inhabit is really in 

 the case of successively finding itself subjected to 

 different climates." He then exclaims in eloquent, 

 profound, and impassioned language: 



" How curious it is to see that such suppositions 

 receive their confirmation from the consideration of 

 the state of the earth's surface and of its external 

 crust, from that of the nature of certain fossils found 

 in abundance in the northern regions of the earth, 

 and whose analogues now live in warm climates ; 

 finally, in that of the ancient astronomical observa- 

 tions of the Egyptians. 



" Oh, how great is the antiquity of the terrestrial 

 globe, and how small are the ideas of those who at- 

 tribute to the existence of this globe a duration of 

 six thousand and some hundred years since its origin 

 down to our time ! 



" The physico-naturalist and the geologist in this 

 respect see things very differently ; for if they have 

 given the matter the slightest consideration — the one, 

 the nature of fossils spread in such great numbers in 

 all the exposed parts of the globe, both in elevated 

 situations and at considerable depths in the earth ; the 

 other, the number and disposition of the beds, as also 

 the nature and order of the materials which compose 

 the external crust of this globe studied throughout 



* Hooke had previously, in order to explain the presence of tropi- 

 cal fossil shells in England, indulged in a variety of speculations 

 concerning changes in the position of the axis of the earth's rotation, 

 " a shifting of the earth's centre of gravity analogous to the revolu- 

 tions of the magnetic pole, etc." (Lyell's Principles). See also p. 132. 



