602 _. GEOLOGY OF OHIO. 
believed that the clay is the result of the decomposition of the overlying 
Corniferous limestone, and not a product of original deposition. Such 
accumulations are very common along the outcrops of limestone forma- 
tions, and notably, in the seams and crevices of the State quarries, but 
whenever they have this origin, they betray it by the silicious frag- 
ments of rock or fossils that they enclose. The clay here referred to is 
very fine-grained and homogeneous, is either white or red in color and 
contains no recognizable foreign fragments. It may, therefore,-be taken 
to mark a change in the character of the seas in which the underlying 
limestone had so long been forming, and it may ba added that other in- 
dications, derived from their chemical analysis, point in the same direc- 
tion. : | 
Their composition is shown in the following analyses, made for the 
Survey by Professor Wormley, number 1, being the red variety and 
number 2, the white variety just named. Both samples were taken 
from the bank of Big Darby on the John Phillips farm, one mile below © 
Georgesville: 
1 Os 
STING TCA Ke Kes Cd AEA en EEN COE Se Ge CED DORN TEAM Cahn Rome s Ce Suen Re TS Lagbels bt he 0 48.11 35.30 
SAT USTYUN TRE oe eee CU Rea Na EAC Iai Pe gc vA MI gL pte PR gos eR 30.30 9,50 
SSCS OF Ibo. sodbbsscsetosood besaes sH50 Bee Sn Okan 6.70 Trace 
LEAR Bee says BY pest iy SOMO el AEE ah NL le cai ce CA nt cp .60 00 
U4 LEP KET Ete HN elias MMe Ee ier Lae EA eK A eR hs SS aa 83 23.03 
Sodan GePotas iy Ase ie he CEs eS SERRE ea PEt fiee hae Sap ee Re We a5) 
NAGY 2) Say Mie ly eae ae na SR any a NA Ses RR Sms AIC, Ae iA 7.65 32.35 
100.46 100.93 
The dissimilarily in composition is so great as to forbid their reference 
to a common origin and especially to the weathering of the adjacent 
limestone. | 
It has already been remarked that this limestone is magnesian in 
character. The compos:tion of some of its phases is shown in the fol- 
lowing analyses. It may be added that the concretionary masses give 
promise of making a hydraulic cement. At least they do not readily 
burn into lime: 
1 2. 3 4 
Insolullenmatten. sss. sccm ece soe 1.10 £0 .20 40 
Caionater che ibime ses saeaeareeeer 64.20 55.20 47.20 55,00 
Carbonate of Maguesia....--..--.--- 34.44 43.58 Al 82 44.10 
99.74 99.58 99.32 99.50 
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