264 DR. THOMAS STERRY HUNT ON THE 
member of that series, and was included with it by Emmons in his Upper Taconic division. 
Emmons now read aright the relations of these rocks, and saw that the sections in which 
the limestones appear to underlie the massive green sandstones give an inverted success- 
sion. Logan, however, though recognizing therein the existence, in many cases, of over- 
turned anticlinals, inverted the whole series, and regarded the basal or Sillery sandstone 
as the highest member, while the Levis limestones were made the lowest. 
§ 123. This erroneous view as to the succession of the strata at Quebec, at first declared 
by Logan to be merely provisional, was the more acceptable for the reason that it could be 
made to accord with the hypothesis that the adjacent crystalline schists were, as Mather had 
taught, the altered equivalents of what was now called the Quebec group. When, as 
is sometimes the case, the Nillery sandstone was found alone (as long before described by 
Emmons,) resting upon the crystalline schists, the higher and softer members of the gray- 
wacke-series having disappeared, Logan supposed that these schists were no other than 
shales of the Sillery (and Lauzon) in an altered and so-called metamorphic condition,-—which, 
according to his view of the succession, should underlie these sandstones. Hence, it was 
that the Huronian rocks of the Notre Dame range, (the prolongation of the Green Mountains,) 
were by Logan called altered Quebec group, long after it had been shown by the present 
writer, that fragments of these same eozoic rocks occur in conglomerates with the fossili- 
ferous strata of the Levis division near Quebec. 
§ 124. In like manner, when the Nillery sandstone was found, farther southward along 
the Graywacke-belt, to rest upon the Taconian marbles and slates, these were by Logan 
declared to be limestones and shales of the Levis division in an altered condition (116). But 
this was not all :—as the Levis beds, sometimes through inverted faults, and sometimes 
through dislocations, came to be placed beneath the Nillery, so the black Ordovician slates, 
whether in direct contact with the Cambrian, or with the older rocks, were, as the result of 
similar accidents, made to underlie the more ancient groups of strata, and were believed by 
Logan to be older than these. In either case, his argument was the same: in the former, 
these Ordovician strata were Potsdam beds passing beneath the unaltered Quebec group ; 
and in the latter, they were the same beds underlying the altered strata of the same 

Quebec group. 
§ 125. To complete this history, we must recall the fact, that not content with including 
in the newly-organized Quebec group, besides the Cambrian Gray wacke,with its limestones, 
the Taconian and the Huronian of the Atlantic belt, Logan proposed to extend it to Lake © 
Superior. Assuming that the horizontal sandstones there overlying unconformably the 
Keweenian or copper-bearing series, were of the age of the Chazy or St. Peter’s sandstone 
of the upper Misissippi, Logan was led to assign the whole of this series of 20,000 feet to- 
the Quebec group, and thus to give it a position above the horizon of the fossiliferous Pots- 
dam sandstone of Wisconsin and Minnesota; which, as seen on the St. Croix River, and 
elsewhere in that region, is well known to overlie the Keeweenian unconformably, and 
is probably separated from it by a great interval of time. This view will be found repre- 
sented on Logan’s small map of Canada, dated 1864, and also in his larger map, of 1866. 
The group of bluish argillites, with quartzites, magnetite and limestones, found on Thunder 
Bay and the Kamanistiqua River, ()89) which was believed by Logan to underlie the 
Keweenian, was not distinguished from it on the map in question, but was supposed by 
him to represent the Potsdam, from which, it is unnecessary to say, it is wholly distinct. 

