672 KANSAS CITY REVIEW OF SCIENCE. 



held in situ. Second, the siUca was present from the first formation of the rocks, 

 having been collected by Polycystines, Diatoms, the spicules of Sponges, etc. 

 Third, the silica was present from the first formation of the rocks, but was de- 

 posited by physical and chemical means, rather than by the intervention of life. 

 The first hypothesis is objectionable because it seems inadequate. It is dif- 

 ficult to conceive of conditions under which great strata of limestone could be 

 completely silicified without altering those in direct contact with them. It is 

 true, the purest limestone in this locality contains silica; some specimens may be 

 found containing a large per cent, of it, but there is no trouble whatever in dis- 

 tinguishing the Umestone from the chert. In other words, so far as has been ob- 

 served, there is positively no gradation of the one into the other, as would neces- 

 sarily be the case had the above mentioned metamorphic action taken place. 

 The occurrence of the concretions and the chert so far above the limestone hor- 

 izon, would be impossible by this theory, unless we conclude that here the change 

 from the limestone to the chert was complete. But it is hardly possible that the 

 transformation act would have been so complete here and so incomplete in other 

 places. Again, the condition of the fossil crinoids has a testimony of value. 

 Had they been imbedded in limestone, it is hardly probable that the limestone 

 itself would have been completely changed to tlie most compact chert without 

 the same action affecting them sensibly. If we assume, however, that the body 

 of the rock was chert when it was first formed, we can easily see how the central 

 cavity of the crinoid stem would be filled with silica, and how the body of the 

 stem itself, long after the rock had become a compact mass of flint, could be re- 

 moved by the solvent action of» water, the most solid rock being penetrated by 

 water. The fact that in the same mass of chert one portion has been filled with 

 crinoids, and the other portion has contained none, may also throw light upon 

 the subject. It is quite possible for a mass of silicic acid, were it present in suffi- 

 cient quantity, to settle to the bottom of the water in which it was suspended, 

 completely cover up and enclose within its mass all the shells which were present, 

 so that the lower portion of the rock thus formed would be filled with shells, 

 while the upper portion would be free from them. If, then, there is any action 

 between silicic acid and calcium carbonate, some of the shells would be silicified. 

 The facts observed exactly correspond to such an hypothesis. 



It is well known that waters charged with silicic acid do affect limestone and 

 calcareous shells. Prof. Patrick* of Kansas State University, has shown that 

 such an action has taken place at the Great Spirit Spring, near Cawker City, 

 Kan. Churchf had occasion to investigate this subject in his researches with 

 reference to the origin of beekite, a peculiarly mineralized fossil quite common in 

 some parts of England, He passed water containing carbonic oxide and silicic 

 acid in solution, through a piece of coral fitted into the neck of a funnel. The 

 porosity of the coral permitted the water slowly to pass through. Almost the 

 whole of the silica was deposited on the coral in a jelly like mass, while a cor- 



*Trans. Kan. Acad. Sci. Vol. 7, P. 22. 

 fL. E. & D. Phil. Mag. (4) Vol. 23, P. 95. 



