GEOLOGICAL EXPLORATIONS AND LITERATURE. 57 



(1) As to the structural relatious and origin of the iron ores and asso- 

 ciated jaspers: 



The observations anil fignres given in the preceding text show conclusively that 

 the statements of Messrs. Dana, Kiinl)all, Hunt, Brooks, and others, that the iron ore 

 is interstratitied in the associated schists, are incorrect, and only return to the view 

 advocated by ^Ir. Fctster in his early publication. 80 far as geological science has 

 now advanced, the facts observed can only be explained by the eruptive origin ot 

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

 conclusion is the supposition that the ore and jasper have been rendered plastic in 

 situ, while the chloritic scliist has not been. Such a supposition Mr. Brooks' was 

 forced in part to. adopt. Tliat the ore and jasper have been thus rendered plastic, 

 while the schists, quartzites, and other associateil rocks have not been, is too absurd, 

 chemically or geologically, to be tolerated for a moment as an hypothesi.s. . . . 

 The ore and jasper show that they are the intrusive bodies by their breaking across 

 the lamination of the schists and other rocks, by the cliauges that take place in the 

 latter at the line of junction, by horses of schist being inclosed in the ore, by the 

 curvature of the huniuation 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 

 jasi)er was seen. That the present lamination of the schist existed jirior to the intru- 

 sion of the ore and jasper is shown by the elfect 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; but whether it is or not, it has been taken to be such by the observers 

 quoted in the establishment of their theories, and they must abide by it. The 

 lamination, however, coincides with many of the well stratified rocks adjacent, 

 and in some of these the ore and jasper were unmistakably intrusive. The 

 schists that retained well marked stratificatiou planes showed in some places extra- 

 ordinary contortions, one specimen (29.')) showing a synclinal and ai'ticlinal fold, 

 reiiniring, were the top eroded, the counting of the same layer four times in the 

 width of 2 inches. This is only one case out of numerous ones observed (292, 292+, 

 302). In the fine grained detritus composing some of the schists it is (juite likely true 

 that the lamination does not coincide with the original bedding; but if it docs not, 

 then the breaking of the ore across any chosen plane whatsoever, except the lamina- 

 tion plane, can be shown more easily than in the former case. 



The ore and jasper seem to have been erupted in huge bosses and overflows, as 

 well as intruded into the schist in the form of long arm and wedge like masses or 

 sheets. On account of the banded character of the jasper, and the intrusion gener- 

 ally being nearly in line of the lamination in the large mass, they have an apparently 

 stratified character to those who believe any "striped" rock is a sedimentary one; 



'Geol. of Mich., vol. i, 1873, pp. 139, 110. 



