MACKIE REMNANTS OF THE FIRST LIFE-WORLD. 287 



masses were erupted, or protruded through sedimentary strata, the 

 mere knowledge of their existence is nearly or quite valueless as 

 evidence. 



The Canadian divisions of the Bottom Eocks " have received tho 

 appellations of Laurentian" and Huronian." 



Por 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 tho 

 geology of Canada, and to a little volume published about three years 

 since in Paris, Esquisse Geologiqiie du Canada," by MM. Logan 

 and S terry Hunt. 



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 Laurentines — 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 

 southernly 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 

 forms the eastern margin up to the 47th degree of latitude. Quitting 

 the lakes, the range extends in a north-westward direction to tho 

 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 IT.E. and S.W. 



The shores of Lakes Huron and Superior offer a scries 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 *4he Huronian" — are inferior to^ or below the Silurian 



