No. I.] GEOGNOSTICAL OBSERVATIONS. 519 



and in process of time a border of spurious peat is formed round the various 

 bays of the lake. 



Moose Deer Island, and the islands adjoining to it, seem to be on the 

 boundary of the limestone formation which we have so often mentioned. Large 

 fragments of the stones containing shells were imbedded in the soil ; and al- 

 though we did not discover any of the rocks in situ, yet the form of the rising 

 grounds, on the different islands, strongly countenanced the opinion that the 

 strata underneath consisted of limestone. The stone, from Mr. WentzePs infor- 

 mation, occurs in horizontal strata, traversing the bed of the Rivifre aux Liards, 

 (the south branch of M'Kenzie's River,) and betwixt that and Slave Lake 

 near the Trout River there is an extensive plain of white earthy marl, similar 



to that which we observed at Pierre au Calumet, on Athabasca River, asso- 

 ciated with the limestone. Farther down M'Kenzie's River, and more to the 

 westward, the coal formation exists. There are beds of coal on fire twenty or 

 thirty miles above the influx of Great Bear Lake River, and below that there 

 are petroleum and sulphur springs. 



Reverting again to our route. Primitive rocks occur a little to the eastward 

 of Riviere d Jean, one of the many channels by which Slave River pours its 

 waters into the lake. Stony Island is a small naked rock rising fifty or sixty 

 feet above the water, and precipitous on the north side. It is a mass of granite 

 consisting of flesh-coloured felspar and quartz, with but little or no mica. The 

 Rein-deer Islands, which lie in the traverse to the north side of the lake, con- 

 sist of a much coarser granite with the mica in large plates. These islands 

 are numerous, and rise from a hundred to two hundred feet above the water. 

 They abound in precipices, and are for the most part naked ; but towards 

 the centres of the larger ones, there is a little soil and a few groves of pine. 

 The same kind of granite prevails on the northern shores of the lake, from 

 the Big Cape to some distance to the westward of Fort Providence. It forms 

 small hills, with steep, somewhat precipitous, sides, and narrow valleys be- 



tween. 



The lower part of these hills generally consists of coarse granite, much in- 

 tersected by veins of quartz and felspar, and frequently enclosing- masses of fel- 

 spar ; their summits, on the contrary, mostly smooth and rounded, never peaked, 

 are formed of a more compact and durable rock, which is the same kind of gra- 

 nite that is observed at Fort Chipewyan, and is composed of a crystallized red 



