294 Chemical Origin of Iron Ores, Etc. — Winchell 
The objections to the eruptive hypothesis of Foster and 
Whitney, lately revived by Dr. Wadsworth, have been stated 
in the fifteenth report of the Minnesota survey, and it is not 
necessary to dwell on them here. The extreme length to 
which Dr. Wadsworth is carried by his predilections for eruptive 
agencies is seen in his arguing ' that the quartzyte at Republic 
mountain is eruptive. One of the chief obstacles to this theo- 
ry is the novelty of the proposition to enclose fused silica in 
the same mass with crystalline hematite and require them to 
cool without chemical union, the former retaining an amor- 
phous state and the latter not losing its crystalline structure. 
Another obstacle is the plainly sedimentary banding that the 
ore presents — i. e. the jaspilyte — which is unlike any structure 
known to result from the cooling of molten rock, and which 
unmistakably reveals the action of water in the formation of 
long parallel bands or strata. 
The difficulties in applying the theory of Irving, i. e. the 
metasomatic substitution of oxides of iron for some preexist- 
ing carbonate, appear when we search for the remains of the 
supposed older carbonate, and when we find the country rock 
does not afford good reason to have expected the deposition of 
any carbonate ; and also when we search for the remaining 
ingredients which the assumed metasomatic process may have 
left in the ore. In short, the whole mass of geological and 
mineralogical environment, as seen in the Huronian rocks, is 
at variance with that seen in the Keewatin, and precludes the 
hypothesis that ordinary chemical substitution will account 
for the chalcedonic silica and the hematite of the jaspilyte 
lodes. 
But that chemical processesplayedaprominentif not a prin- 
cipal part in the formation of the jaspilyte, and in the meta- 
morphism of the strata of all the Archean, there is no dispo- 
sition to call in question.** It is here appealed to as the prime 
agent in giving origin to the chalcedonic silica and the iron 
ore of the jaspilyte. 
In order that the physical circumstances which obtained 
during the age of the crystalline and sub-crystalline schists, 
* These results are based on average analyses for 1888, published by 
Pickands, Mather & Co., derived from several thousand assays. 
' Notes on the Geology of the Iron and Copper districts. Bui. Mus. 
Comp. Zool.., Geol. ser. vol. i. p. 64. 
* A. Winchell. Fifteenth Report Minnesota survey, p. 196. 
