On the Fossil Shells of the Paris Basin. 221 



beings ; but we will not urge this interesting subject, which 

 demands more attention than we could devote to it in this 

 place. 



The details we have gone over, appear to lead to the fol- 

 lowing conclusions : — ■ 



The first tertiary period must have rolled away under an 

 equatorial temperature, in all probability, many degrees 

 warmer than that of the present equator. 



During the second period, the deposits of which occupy 

 the centre of Europe, the temperature has been similar to 

 that of Senegal and of Guinea. 



The temperature of the third period was at first a little 

 higher than that of the present basin of the Mediterranean, 

 it then became, as we have endeavoured to shew, fixed 

 or uniform : for in the north, the species of the north are 

 fossil ; in the south those of the south are fossil. 



Thus we have established the fact, that since the com- 

 mencement of the tertiary beds, the temperature has been 

 constantly diminishing: the theory of the central heat of 

 the globe, which rested on the supposition of philosophers, 

 rendered the change of temperature, of which we have been 

 speaking, probable; but it is curious to see a science long 

 neglected approaching these important questions, and fur- 

 nishing materials calculated to explain them. 



The question of temperature is not the only domain of 

 Zoology and Conchology in particular, its use extends to 

 other subjects of no less importance, connected with the 

 development of life on the surface of the earth, throughout 

 time and space, in proportion to the extent of its materials ; 

 but this science is yet in its infancy. Lamarck has drawn 

 the outline ; who is to lay the foundation ? 



We have long since remarked, and we continue to repeat, 

 that Geology had no claim to the character of an exact 

 science until the moment when she adopted those branches 

 of philosophy which treat of organic beings, their investiga- 



2 G 



