MACKIE — REMNANTS OF THE FIRST LTrE--\A'ORLD. 287 
masses were erupted, or protruded through sedimentary strata, the 
mere knowledge of their existence is nearly or quite valuclesa as 
evidence. 
The Canadian divisions of the " Bottom Eocks " have received the 
appellations of '■' Laurentian" and " Huronian." 
For the knowledge of these and of the nature and sequence of the 
overlying rocks we are mainly indebted to Sir W. E. Logan, and we 
refer those of our readers who desire more detailed information of this 
subject, of which we give a resume, to Sir "William's reports on the 
geology of Canada, and to a little volume published about three years 
since in Paris, " Esquisso Gcologique dii Canada," by MM. Logan 
and Sterry ITunt. 
The province of Canada is divided in its entire length by a moun- 
tainous tract which divides it into two basins. These mountains are 
known as the Laurentincs — and hence the first appellation—- 
from the northern bank of the river St. Lawrence, from the 
Gulf to Cape Torment, near Quebec, from which point, gradually 
diverging from the course of the stream, they form, in their range west- 
ward, the high land along the line of Outaouais, and pass near Cat 
Lake, at about one hundred and fifty miles from Montreal. Taking a 
soutliernly direction, they regain the St. Lawrence near the discharge of 
the Lake Ontario, and thence run to the north-west ; the south-eastern 
extremity of this range being attained at Lake Huron, of which it 
forma the eastern margin up to the 47th degree of latitude. Quitting 
the lakes, the range extends in a north-westward direction to the 
Arctic Sea. 
These rocks, for the most part gneissic or hornblendic schists, are the 
oldest in America, corresponding to the Scandinavian gneiss and the 
similar rocks of the North of Scotland, and attain in this vast range a 
height of 2,500 to 3,000 feet or more. They are, without exception, 
ancient sedimentary deposits, which have become highly crystalline, and 
have been subjected to great disturbances ; the general direction of the 
mountain ranges being N.E. and S.W. 
The shores of Lakes Huron and Superior offer a series of schists, 
limestones, and conglomerates, intercalated with which are thick masses 
of diorite, reposing unconformably upon the rock-masses of the Lauren- 
tian formation. These rocks — called from their typical development in 
this region "the Huronian" — are inferior to, or below the Silurian 
