“ s 
d 
184 Association of American Geologists. e 
mica, talcose and clay slates. These hills have a general easterlyand 
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 
Michigan. 
The trap rock, which chiefly appears as a compact greenstone, 1s 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 0 
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 ata 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 impossr 
ble to convey a clear conception of its geographical geology, and that m 
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, tran® 
ported masses of native copper are occasionally met with, in the dilavial 
deposits which are so abundantly spread over the country; and wo 
loose masses are distributed over an area of many thousand miles, inclu- 
ding southern Michigan, Wisconsin, Illinois and Indiana. In northerB 
Michigan they are still more frequently met with. 
The great transported mass of native copper on the Ontonagan 
so frequently alluded to by travellers, and which he, Dr. H., estimated t0 
contain about four tons of native metal, was stated to have all the chara’ 
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 OF oh 
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 4 very 
considerable portion of them had their origin from what may be regarded 
as true veins. — ; 
Poe 
%, 
river, 
