MUSEUM OF COMPARATIVE ZOOLOGY. 67 



others, that the iron ore is iuterstratified in the associated schists, 

 are incorrect, and only return to the view advocated by Mr. Foster in 

 his early publication. So for as geological science has now advanced, 

 the focts 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 conclusion is the supposition that the ore and jasper have been 

 rendered plastic in situ, while the chloritic schist has not been. Such a 

 supposition Mr. Brooks was forced in part to adopt.* 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 geo- 

 logically, to be tolerated for a moment as an hypothesis. Should it or 

 any other theory be proved to be con-ect in actual fact, then it is to be 

 admitted; but when one resorts to theories that are not sound scientifi- 

 cally, merely to escape from a dilemma that a. former theory brings him 

 to, he is neither philosophical nor scientific. Theories must conform to 

 facts, not the facts to the theory. We can point out facts whether they 

 can be explained or not, but the theory must conform to our present 

 knowledge. 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 changes that take place in the latter at the line of junction, by horses 

 of schist being enclosed in 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 present lamination of the schist existed prior 

 to the intrusion of the ore and jasper is shown by the effect 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 estab- 

 lishment 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 stratification planes showed in some 

 places extraordinary contortions, one specimen (293) showing a syn- 

 clinal and anticlinal fold, requiring, were the top eroded, the counting 

 of the same layer four times in the width of two 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 quite likely true that 

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

 not, then the breaking of the ore across any chosen plane whatsoever, 

 * Geol. of Mich., I. 139, 140. 



