Mesozoic and Cceaozoic Geology and Palceontology. 41 



the deep depressions, the eastern, the northwestern, and the south- 

 western basins. An intermediate baud of gra}^ ooze occurs in the 

 Athxntic at depths averaging perhaps from 2,100 to 2,300 fathoms. 



" Over the red-chi}' area, as might have been expected from the 

 mode of formation of the red clay, the pieces of pumice and the re- 

 cognizable mineral fragments were found in greater abundance; for 

 there deposition takes place much more slowl}', and foreign bodies are 

 less readil}' overwhelmed and masked; so abundant are such fragments 

 in some places, that the fine amorphous matter, which may be regarded 

 as the ultimate and universal basis of the deposit, appears to be 

 present only in small proportion. 



" The clay which covers, broadly speaking, the bottom of the sea at 

 depths greater than 2,000 fathoms, Mr. Murray considers to be pro- 

 duced, as we know most other clays to be, by the decomposition of 

 feldspathic minerals; and 1 now believe that he is in the main right. 

 I can not, however, doubt that were pumice and other volcanic pro- 

 ducts entirely absent, there would still be an impalpable rain over the 

 ocean-floor of the mineral matter, which we know must be set free, and 

 must enter into more stable combinations, through the decomposition 

 of the multitudes of organized beings which swarm in the successive 

 layers of the sea; and I am still inclined to refer to this source a great 

 part of the molecular matter which always forms a considerable part 

 of a red- clay microscopic preparation." 



It is quite clear, that it would require millions of years for an ac- 

 cumulation to take place two miles in thickness, at the progress now 

 in operation in the Atlantic, at depths from three to five miles. And 

 one can not help thinking that such deposits bear strong resemblance 

 to the red sandstones of the Jurassic and Triassic strata, and conclud- 

 ing, unless there is some reason to be drawn from other sources, to in- 

 fer a more rapid deposition in the formation of the latter strata than 

 that which prevails at the present time, that one is the representative 

 of the other as to the depth of the ocean and the material and method 

 of the deposit. If this be so, the Triassic and Jurassic rocks represent 

 an age of vastly greater duration than the combined Cretaceous, 

 Tertiarj'- and Post-pliocene periods. 



PaljBontolog}' vci^y not follow such a comparison all the way to the 

 final conclusion, but it walks hand in hand so far that we are at a loss 

 to imagine where the separation ma}^ be made. There are many 

 classes and orders of animals that never find a tomb in the great 

 depths of the Atlantic, there are others that start for that goal but 

 reach it only in the shape of an impalpable powder, " the insoluble 



