184 Association of American Geologists. 



mica, talcose and clay slates. These hills have a general easterly and 

 westerly direction. 



Northerly from these, other ranges of hills occur, having a similar direc- 

 tion, but in the several ranges as we proceed north, the granitic character 

 becomes less and less perfectly defined, being first sienitic, after this 

 altered sienite, and finally the outer or northern range is made up of 

 well defined trap. This range of trap hills continues very nearly unbro- 

 ken for a distance of one hundred and thirty five miles within the limits of 

 Micliigan. 



The trap rock, which chiefly appears as a compact greenstone, is nev- 

 ertheless, quite uniformly bounded on the north by an amygdaloid, against 

 or upon which rests a very coarse conglomerate, and upon this a series of 

 alternating strata of conglomerate and sandstone, the whole being capped 

 by an extensive formation of red sandstone. 



The group of stratified rocks referred to, which have an entire thick- 

 ness of several thousand feet, dip very regularly, and usually at a high 

 angle, into the basin of Lake Superior ; and since the same is the fact in 

 regard to the rocks upon the north coast, that lake may be said to occupy 

 a synclinal basin. 



After some remarks upon the successive elevation of the several ranges 

 of hills referred to, together with the long intervals of time that would 

 appear to have elapsed between the several uplifts, Dr. H. proceeded to 

 say, that with our present imperfect maps, it would be nearly impossi- 

 ble to convey a clear conception of its geographical geology, and that in 

 fact he had made these references, only to render more intelligible what 

 he wished to say upon the subject of the metalliferous veins of the dis- 

 trict. 



It is a fact well known, that south from the district referred to, trans- 

 ported masses of native copper are occasionally met with, in the diluvial 

 deposits which are so abundantly spread over the country ; and these 

 loose masses are distributed over an area of many thousand miles, inclu- 

 ding southern Michigan, Wisconsin, Illinois and Indiana. In northern 

 Michigan they are still more frequently met with. 



The great transported mass of native copper on the Ontonagan river, 

 so frequently alluded to by travellers, and which he, Dr. H., estimated to 

 contain about four tons of native metal, was stated to have all the charac- 

 ters of the other loose masses referred to. 



The source of these transported masses has, heretofore, been somewhat 

 obscure, although there has been good reason to believe, that most of them 

 had their origin from the trap rocks, but whether from true veins or from 

 the mass of the rock itself, was not known. He said that after examining 

 the country with care, he was enabled to state, that without doubt a very 

 considerable portion of them had their origin from what may be regarded 

 as true veins. 



