THE GEOLOGICAL RECORD. 137 



pretty conclusively 1 . From this point, however, up to 

 the Great Oolite, Mr. Parfitt tells us that scarcely a 

 vestige of the sponges is to be found, although since 

 that time they have been very abundant. Between the 

 Silurian and the Great Oolite the interval of time must 

 have been enormous. It is occupied by a vast series 

 of sedimentary rocks, embracing very varied mineral 

 characteristics. From this series our museums have 

 been, and are still being, supplied with vast heaps of 

 fossil organic structures, including among numerous 

 others, plants and corals and fish and reptiles. Through 

 all that protracted period there is no reason to 

 suppose, in regard to the outer rind of the globe, 

 that the general conditions of earth, air, and 

 water were other than they are now. All England 

 may have been under water; delicate creatures may 

 have wintered at the North Pole for the sake of its 

 genial climate ; and an infinity of other local and 

 temporary differences may have prevailed, without 

 making the habitable globe of those days essentially 

 different from our own. The laws of chemistry and 

 mechanics, the laws of heat and motion, must have been 

 just the same as they are now. Then, as now, there 

 must have been oceans and continents, winds and 

 currents, forests growing, decaying, and being buried, 

 sand and chalk being deposited in layers, molten 

 minerals thrown up by volcanoes, ice forming at a 



1 See Mr. Pengelly's paper on the subject in the Transactions of the 

 Devonshire Association for 1868. 



