GEOLOGICAL EXPLORATIONS AND LITEKATUliE— LSSO. 77 



He g-ives as liis reasons for this concliisioii tlie observations that tlie 

 sandstones were "found to contoi-m in their stratification to tlic contour of 

 tlie whole mass" of ])eridotite; that the lower portions of the; overlying- 

 rock are altered, as though by the action of heat and heateil waters; the 

 absence of pebbles and fragments of the peridotite from the conglomerates 

 of the sandstones. The serpentine northwest of Ishpeming, first mentioned 

 by Wright, from its microscopic features is thought by Wadsworth to be 

 an altered peridotite. 



The author sununarizes his work antl conclusions in a few pages, from 

 which we extract these passages: 



Tbe observations aud fij;ures nivcii in the prececliug' test sbow conclusively that 

 the statements of Messrs. Dami, Kimball, Hunt, Brooks, and others, that th(^ iion ore 

 is interstratified in the a&sociated schists, are incorrect, and only return to the view 

 advocated by Mr. Foster in his early publication. So far as geologic science has now 

 advanced, the facts observed can only be explained by the eruptive origin of both the 

 ore and jasper, as they make the same formation. The only escape from this conclu- 

 sion is the supposition that the ore and jasper have been rendered plastic in situ, while 

 the chlorite-schist has not been. * * * That the ore and jasper have been thus 

 rendered plastic, while the schists, quartzites, and other associated rocks have not 

 been, is too absurd, chemically or geologically, to be tolerated for a moment as an 

 hypothesis. * * * The ore and jasper show that they are the intrusive bodies by 

 their breaking across the lamination of the schists aud other rocks, bj' the changes 

 that take place in the latter at the line of junction, by horses of schist being inclosed 

 ill the ore, by the curvature of the lamination produced by the intrusion of the ore 

 and jasper, etc. Not the slightest sign of the plasticity or intrusion of the schists 

 relative to the ore or jasper was seen. That the ])resent lamination of the schist 

 existed prior to the intrusion of the ore and jasper is shown by the ettect of the latter 

 upon and its relations to it. That this lamination is the original plane of deposition is 

 for part of the schists not known ; * * * The lamination, however, coincides with 

 many of the well-stratified rocks adjacent, aud in some of these the ore aud jasper 

 were unmistakably intrusive. * * * In the tiner-grained detritus composing some 

 of the schists it is quite likely true that the lamination does not coincide with the 

 origiual bedding; but if it does not, then the breaking of the ore across any chosen 

 plane whatsoever, except the lamination plane, can be shown more easily than in the 

 former case. * * * We are well aware that objections from a metallurgical or 

 chemical standpoint have been raised against the theory of the eruptive origin of 

 hematite and silica together, in such forms as we now find them. If the ore was 

 magnetic at the time of eruption, and has since been altered, this objection is then 



