158 CHALK AND OOZE. [CH. Ill 



III. The third argument is of equal force, or perhaps 

 of greater force, than the last. If the great ocean depths 

 have not always been permanent we should expect to 

 meet with, among the stratified rocks, evidence of deep-sea 

 deposits. Here again defective knowledge offers a way 

 out of the difficulty to those who choose to believe in a 

 thorough change from time to time of the existing 

 relations between continental areas and the great oceans ; 

 the fact that no continental deposits present any likeness 

 to deep-sea " oozes " and " clays " seems to prevent the 

 holding of such a theory ; but the matter requires to be 

 more thoroughly disproved. An exploration of certain 

 geologically little known tracts might reveal evidence in 

 favour of the view which is at present not forthcoming. 

 It was at one time held that there is a great likeness 

 between the chalk of the Mesozoic epoch and the globi- 

 gerina ooze now in course of deposition in certain tracts of 

 the ocean. Superficially this resemblance is not a little 

 striking; but a closer comparison dissipates the theory. 

 It is true that in the deep sea in regions where the 

 globigerina ooze is found certain animals exist which 

 are identical with or very closely allied to animals 

 characteristic of the chalk. The Echinoids with flexible 

 tests, numerous Cidarids, and the species of the Globi- 

 gerinse themselves bear out this statement. A careful 

 analysis however of the chemical composition of the ooze 

 and a comparison of the results thus obtained show 

 divergences which are of importance. The percentage 

 of carbonate of lime in chalk is from 94 98 / , while 



