164 LIGHT SCIENCE FOR LEISURE HOURS. 



the minute races came into being which formed the 

 cretaceous stratum, might be a question. But no 

 doubt existed in the minds of geologists that each 

 formation belonged to a distinct period. Now, how- 

 ever, Dr. Carpenter and Professor Thomson may 

 fairly say, " We have changed, all this." It has 

 been found that at points of the sea-bottom only eight 

 or ten miles apart, there may be in progress the 

 formati6n of a cretaceous deposit and of a sandstone 

 region, each with its own proper fauna. " Wherever 

 similar conditions are found upon the dry land of the 

 present day," remarks Dr. Carpenter, "it has been 

 supposed that the formation of chalk and the for- 

 mation of sandstone must have been separated from 

 each other by long periods, and the discovery that 

 they may actually coexist upon adjacent surfaces has 

 done no less than strike at the very root of the 

 customary assumptions with regard to geological 

 time." * 



Even more interesting, perhaps, to many, are the 

 results which have been obtained respecting the vary- 

 ing temperatures of deep-sea regions. The peculiarity 

 just considered is, indeed, a consequence of such varia- 

 tions ; but the fact itself is at least as interesting as 

 the consequences which flow from it. It throws light 



* This opinion Dr. Carpenter has since somewhat modified. It will 

 be remembered, of course, that the evidence derived from the nature of 

 superposed strata is in no way affected by what is shown above to hold 

 sis respects adjacent deposits. 



