78 THE MARQUETTE IRON-BEARING DISTRICT. 



(lone away with. The sccoiulaiy cbauges that have occurred in the rock since eruption, 

 as shown by microscopic examination, may also help. It is well known that there are 

 facts in every science that it is not able to explain at any one given time; but the facts 

 exist the same, and the s(^ience in time rises to meet them. So in this case the fact is 

 they are eruptive, and the burden of chemical explanation rests upoTi the chemist, not 

 upon us. He must explain it sooner or later, unless he disproves our observations. 

 Crystals of hematite crystallizing from the molten magma of trachytes and rhyolites 

 have long been known, and are described in all the standard works of micro-lithology. 

 These then offer the same problem, and prove that hematite can be crystallized 

 directly out of the same molten magma, and at the same time with the sihca and 

 silicates. It is the business of the chemist to meet the facts, and not for us to make 

 the facts conform to his knowledge or theories. 



We have found that a large proportion of the rocks said to be iiiterstratified, 

 and to pass by insensible (or any other) transitions into the adjacent rocks, are 

 eruptive, and do not so pass into the country rock. The assumption that they were 

 stratified was based on their foliation being parallel to their walls, on their being 

 intrusive approximately parallel to the lamination of the schists, [and on] their gen- 

 eral resemblance to the country rock of similar composition * * *. The intrusive 

 rocks belong in general to the basalts, but are of course old, and in the majority of 

 cases greatly altered. One probable andesite as well as intrusive felsites (rhyolites) 

 was discovered. » * * 



The "soft hematites" are doubtless produced by the decomposition of the jasper 

 and its ore, brought about by the fracturing of the rocks by the intrusives and by the 

 secondary action of water, presumably hot, on account of the microscopic characters 

 of the quartz deposited by it. Besides the "soft hematites" there occur the quartzites 

 and conglomerates derived from the ore and jasper, as well as the sandstones and 

 schists impregnated by iron, which are sometimes mixed to a slight extent. 



We have heretofore seen that the view that the " Huroniau " unconformably over- 

 lies the "Laurentian" has been only supported by the fact that the foliation of the 

 latter did uot conform in its dip to the lamination of the former. This proof is of no 

 value unless it can be shown that both rocks are stratified and in situ. That the latter 

 is uot so, we have seen in numerous localities. Heretofore the two systems have not 

 been observed in contact, but recently statements have been published that their 

 junctions have been seen in other regions. * * * 



So far as the Marquette district is concerned we have shown very much stronger 

 and more abundant evidence to prove that the "Laurentian'' granite is younger than 

 the "Huronian," and an eruptive rock, than has been advanced by Mr. Brooks (the 

 only man who has advanced anything called proof) to show that it is older. * • » 

 (Pp. 6G-70.) 



The general structure of the country would seem to be as follows. The schists. 



