Crosby.] 468 [November 7, 



must also have suffered miles of erosion, and have been com- 

 pletely removed from large areas which they once covered ; so 

 that the Eozoic lands, according to this view, are much wider 

 now than at the beginning of the Paleozoic era. But this only 

 augments the difficulty of finding an adequate source for the post- 

 Eozoic sediments ; — a problem which would appear to be espec- 

 ially difficult for Professor Dana, since there are few geologists 

 who now restrict the Eozoic rocks within such narrow limits as 

 he does, extensive formations commonly regarded as Eozoic be- 

 ing referred by him to the Paleozoic. 



It is said that all the stratified rocks exposed on the continents 

 are shallow water deposits, and consequently that the floor of the 

 deep sea has never been elevated to form land. This proposition 

 is more easily stated than demonstrated. Among the crystalline 

 sediments, especially, there are many kinds which, for aught that 

 we can now determine, may very well have had a deep sea ori- 

 gin ; but the subsequent development of crystalline characters 

 has, in most cases, made it impracticable to trace their histories. 

 There is nothing in our great formations of white crystalline 

 limestone, such as that stretching along the western base of the 

 Green Mountains, to indicate that they are shallow water de- 

 posits ; and it is simply begging the question to set them down 

 as such. Their purity and uniformity are favorable to the view 

 that they have not been formed near the land. 



Over considerable areas of the ocean-floor glauconite or green- 

 sand is now accumulating ; and, so far as I am aware, the essen- 

 tial identity of this deposit with the great beds of greensand in 

 the Cretaceous and other formations has not been questioned. 

 It frequently happens that the siliceous organisms always present 

 in the deep sea oozes predominate to such an extent as to give 

 character to the deposit, which then becomes a Diatom or 

 Radiolarian ooze ; and it is difficult to understand why such a 

 deposit is not fairly represented by the well known diatomaceous, 

 or so-called infusorial, earths of Tertiary age, or even by the 

 hornstones and cherts of the older formations. The Radiolarian 

 ooze has been found in the deepest parts of the Pacific, and no- 

 where at a less depth than 2250 fathoms. 



Mr. Wallace, in his " Island Life," contests the generally ac- 

 cepted view that the chalk is a deep sea deposit and that it is the 



