462 REVIEWS—GEOLOGICAL SURVEY OF CANADA. 
the only sure guide by which the one group can be distinguished from the other, 
the study of these becomes an important part of the investigation.” 
The Report furnished by Mr. Murray einbraces the details of a 
very extensive examination of the coast of Lake-Huron, with the 
back country, around the Bruce Mines. The wide area thus included 
in Mr. Murray’s explorations, lies between the Thessalon and Missis- 
sagui rivers, and presents many features of geological interest. One 
of the most striking, perhaps, not only in a scientific, but probably also in 
an economic point of view, is the discovery of a large fault running 
roughly parallel with the Thessalon River, and probably with the 
coast line generally, between that stream and the mouth of the 
Mississagui. To quote from the Report,— 
“Chert beds, very similar in aspect to those just described, are met with on the 
north-east side of the small lake which is tributary to Walker Lake, Between 
those and the nearest approach to the previous beds, [dipping N.E.,] there is a 
distance of no more than a quarter of a mile. They dip to the southwest with a 
slope of thirty-five degrees, and they might well be supposed to be the same beds 
on the opposite side of a synclinal axis. There is some suspicion, however, as 
will be seen from the sequel, that they are higher strata on the north side of a 
great downthrow fault. 
“These beds, in the attitude above mentioned, are seen along the north-east 
side of the lake for a distance of a quarter of a mile; they are followed north- 
ward by a mass of greenstone, and that again by a great display of white quartzite, 
both running parallel with the chert beds. Three quarters of a mile south-east- 
ward, chert beds again appear, dipping to the south-west, with greenstone coming 
out from beneath them, and in this relation they can be traced for two miles to the 
south-east. Here the chert beds are within eight chains of the south-west corner 
of Thessalon Lake, and the greenstone lies between them and the margin. This 
position is about half a mile from Salter’s side-line, but the farther progress of 
the chert beds towards the side-line appears to be interrupted by a mass of white 
quartzite. 
“The low ground on Salter’s side-line, mentioned as occurring to the north of 
the chert ridge first described, forms a hollow of a few chains in width, beyond 
which the mass of white quartzite just alluded to rises pretty sharply, consti- 
tuting a hill which fills the space between the hollow and the lake, with the 
exception of a narrow mass of greenstone at the waters edge, and overlooks the 
low ground on the south margin of Lake Thessalon to the east. 
“ On this low ground there is an interval of marsh, but beyond the marsh there 
is a point about half a mile above the outlet of the lake, where the strata make 
their appearance. They consist of yellowish chert interstratified with impure 
limestone, and they dip S.37 W.+ 19°. The band is about a quarter of a mile 
wide, and it can be traced without much difficulty in a pretty straight line for 
upwards of eight miles down the river to the higher fall, dipping in the same 
direction and nearly at the same inclination the whole way. In this course the 
