90 Mr. EK. T. Harpman—On the Chemical Composition of Chert. 
Anatysis [X, 
Total 
= b Analysis. 
SiO, (insoluble), j ‘ 4 ~ 95°50 95-50 
SiO, (soluble), ; - AME trace - trace 
Fe,0,, . : ° 
GOR \ : : Ol |, Sale 3-56 
CaO, 6 ‘ 4 6 - trace - 
CaCO.,, : : : d 0:66 - 0:66 
FeS, : : . : trace — trace 
Water and organic matter, . 5 0:25 ~ 0:25 
Insoluble residue, . i 6 98°55 = = 
99:87 98-65 99°97 
Specific gravity, 2°628. 
The above is one of the purest specimens of chert I have examined, although 
both from its appearance and its position lying close beneath the Yoredale Shales, 
I was prepared to find a considerable quantity of silicates of alumina and iron 
in it. 
No. 13. Light, gray chert from nodules in the limestone, just below the last— 
' very hard, effervesces slightly with acid. 
ANALYSIS X. 
A i. Total 
Analysis. 
SiO, (insoluble), ° . ‘ - 85:60 85-60 
SiO (soluble in HCl), . 5 1-22 ~ 1-22 
Si0, (soluble in KHO), ‘ 3 - 0:95 0:95 
Fe,0,, 4 : : 
Al.0, : 6 6 : 0°73 2°44 Bly 
FeO, : . 6 : 0:10 _ 0:10 
CaO, ; g 5 ~ 1:09 1-09 
MgO, . - 2:20 2-20 
CaCO,, : . . 4:40 - 4:40 
MgCO,, , ° ; . trace - trace 
Na,O, 5 : 5 ; trace - trace 
Water and organic matter, . 5 1-12 — - 1:12 
Insoluble residue, : z : 92°31 - - 
99°88 92°28 99.85 
Specific gravity, 2°66. 
The small quantity of silica dissolved by a strong solution of potash, is probably 
some hydrated silica, the result of alteration. 
No. 14. Bedded chert from the same horizon as No. 12, and possessing much the 
same characteristics and appearance. 
