Chemical Origin of Iron OreSj Etc. — Wi7ichell. 299 
in one portion of the stratification that nullified those that 
were demanded to produce the rocks of the other. By the 
separation of the Keewatin from the Huronian, a different set 
of conditions may be relied on, but none other thao those 
needed to produce the rocks that are found to compose it. 
It is not the purpose of this paper to explain any of the 
physical conditions of the jaspilyte,nor of the strata that com- 
pose the bulk of the Keewatin, such as brecciation, folding and 
involute contortion, compression, fracturing and transporta- 
tion of strata once formed, the upheaval and prevailing verti- 
cality of the beds. These, in the main, must have been pro- 
duced subsequent to the chemical precipitation here appealed 
to to explain their origination, but to a certain extent seem to 
have been cotemporary with the precipitation of the beds 
themselves. But it is our sole purpose to account for the 
existence of the jaspilyte by some hypothesis consistent with 
known chemical laws, and in accordance with such surround- 
ings and physical forces as the nature of the Keewatin rocks 
shows to have obtained at the time of its formation. This 
hypothesis not only is consistent with these laws and condi- 
tions, but it explains some of the features of the jaspilyte 
which no other theory, so far proposed, will explain. Some 
of these peculiar features may be mentioned, namely : Urst^ It 
accounts for the minutely fine structure of the silica, and for 
the uniformity of its granular texture on disintegration ; 
second, It accounts for the prevalence of this structure at all 
depths in the earth, wherever the jaspilyte is found to extend ; 
third. It accounts for the agate-like banding and the minuter 
lamination that characterize the jaspilyte; fourth. It fur- 
ishes an explanation for the purity of the white chalcedonic 
ribbons, which consist of silica only ; iifth, It explains the 
re-cementation of some of the thin, brecciated layers by 
materialof the same kind as the layer itself; sixth, Itexplains 
the occasional intrusion of rounded grains of non-chalcedonic 
quartz into the mass of chemically precipitated quartz; 
seventh, It explains, lastly, the occasional mingling of chal- 
cedonic silica with the finer elements of the basic schists, 
forming regular sedimentary alternations. 
Sum77iart/. All attempts hitherto made to account for the 
existence of the iron ores of the northwest, particularly those 
of Profs. Irving and Van Hise, have confounded the phenom- 
