612 



ADDENDA. 



shells not existing there. We may also suppose that he had discovered 

 that the limits of the more tropical forms, both animal and vegetable, of 

 the productions of the land, had likewise during this former period 

 extended further south: what, then, would he say? Would he not at 

 once infer, with the strongest appearance of truth, that the climate formerly 

 . had a more tropical character, properly so called, and therefore had a higher 

 annual mean temperature than at present? Nevertheless, we know such 

 an inference would have been absolutely erroneous. To put the case in 

 another point of view : should a geologist find, in lat. 39°, on the coast 

 of Spain, a tertiary deposit, abounding with Olivas, Volutas, and Terebras ; 

 or in lat. 45°, on the coast of France, other beds, containing a large 

 Voluta, and numerous Patellae, Fissurellae, Chitons, and Balani, larger 

 and of stronger growth than the existing species, would he be justified, 

 after what is now known, in pronouncing that the climate formerly had 

 a higher mean temperature ? I think it may be safely asserted that 

 he would not be so justified, but rather would be bound to search for 

 other evidence. In the actual case of Europe, we have knowledge (as will 

 be shown in a following note*) of another element in the problem, 

 namely of the lower descent during former times of the snow-line, — as is 

 inferred from tlie former low descent of glaciers, on the same moun- 

 tains, where they now occur only at great heights, and likewise from 

 the congelation during this same period of the soil in a low latitude — and 

 this new element, I believe, gives the key to the solution of the problem, 

 which is, that the climate of Europe was formerly more equable, but so 

 far from being strictly more tropical, that it probably even had a lower 

 mean annual temperature than it now possesses. I need scarcely say 

 that I here refer only to the later tertiary periods : in the more ancient 

 epochs, the plainest analogies tell us of an equatorial climate, whilst on 

 the other hand, we are very far from having the smallest reason to sup« 

 pose that the snow-line then descended low ; and this is the key, as Ihave 

 called it, to the problem of later times. 



Page 282. 



With respect to ice transporting fragments of rock in the Antarctic 

 regions, M. Cordier, in bis instructions f U Institut, 1837, p. 283^1 to the 

 voyage of the Astrolabe and the Zelee, has this passage : " Les relations 

 de I'expedition anglo-americaine de decouverte executee en 1830, nous ont 



* As these notes are appended to the Journal, I have found it scarcely 

 possible to classify them properly. I have been obliged to allude to the 

 lower descent of the glaciers in Europe during former periods — facts which 

 are first brought forward in a succeeding note to p. 294. 



