THE CHERT ROCKS OF SUBCARBONIFEROUS KANSAS. 673 



responding amount of calcium carbonate was removed. Dr. T. Sterry Hunt* 

 has held that the numerous silicified shells have thus been changed before they 

 were enclosed in the limestone which surrounds them. He describes shells 

 which are only partly silicified, the central portion being unchanged. 



The second hypothesis mentioned is understood to be the generally accepted 

 view. It may fairly be represented by quoting from pages 615 and 691 of Dana's 

 Manual of Geology, 1876: "The silica in most siliceous petrifactions, has 

 come from siliceous organisms associated with the fossil in the original deposit •" 

 and: "The geological effects of silica in cold solutions appear to be of only in- 

 finitesimal importance." There can be no doubt that the spicules of Sponges and 

 the shells of Diatoms and Polycystines, have contributed largely to the silica of the 

 earth's crust. The flint nodules of chalk seem to be almost entirely composed of 

 them. Throughout the whole stratified crust of the earth, we find sandstone and 

 chert formations in great abundance. The sub-carboniferous of Missouri, Ten- 

 nessee, Kentucky, Iowa, Illinois, Indiana, and in general wherever it occurs 

 presents phenomena similar in many respects to those observed in Kansas. Fos- 

 sils imbedded in chert are common to all the above mentioned States. In fully 

 one-third of the State of Tennessee the sub-carboniferous is exposed, the lower* 

 portion of which has been named the "Siliceous Group. "J Portions of the sand- 

 stones are fragmental rocks, which may be traced to granitic and other forms of 

 siliceous rocks. But we can go no farther. We cannot say how the silica came 

 in those rocks, but we have every reason to believe that life had no part in their 

 formation. Other portions of sandstone show, from the perfect crystalline form 

 of their grains, that they are not fragmental, but that the silica has been depos- 

 ited in some manner that favored crystallization, so that organisms are shut out 

 from these. Daubree§ has shown that by the mechanical decomposition of 

 ancient rocks, the proportion of silica left in the form of sand, would be entirely 

 too small for the formation of all the great beds of sandstone ; also that in dif- 

 ferent parts of France a large per cent, of the sandstone is composed of crystal- 

 lized grains. Mr. J. Brainard, at the meeting of the American Association for 

 the Advancement of Science in i860, called attention to certain sandstone in 

 Ohio of crystalline origin. 



It is well known that natural waters frequently hold silica in solution. 

 Deville|| has said that silica was found in all the natural waters which he has ex- 

 amined. M. Ebelman ^, by a careful and exhaustive analysis of basaltic and 

 similar rocks in different degrees of decomposition, has found that the amount of 

 silica rendered soluble by decomposition is as great, in some instances, as 57 per 

 per cent, of the original amount. He compared the alumina with the silica 

 before and after decomposition, and found that in some specimens in which for 



♦Canadian Naturalist, New Series, Vol. 1, P. 46. 



JSafford's Geol. Sur. of Ten. 



gAonals Des Mines (5) Vol. 12, P. 535. 



II Annals de Chtemie et de Physique. Vol. 23, p. 33. 



If Annals des Mines (4). Vol. 6, p. 31. 



