﻿1851 



LOGAN ON SILURIAN FOOT-PRINTS. 



249 



sented to the Provincial Government — those for 

 1845-6 and 1847-8. From these and from the 

 distribution of the rocks in New York, as map- 

 ped and published by the State Survey, the 

 structure will be easily understood. In Canada, 

 a formation, consisting of gneiss and interstrati- 

 fied crystalline limestone, sweeps through the 

 province on the north side of the St. Lawrence 

 and its lakes, from Lake Huron to Labrador. 

 Below Cape Tourment its southern limit lies 

 close upon the river, but above the Cape keeps 

 at a variable distance from it in all parts, with 

 the exception of the Thousand Islands, below 

 Kingston, where the gneiss crosses the river to 

 form a junction with a great peninsula-shaped 

 area of the same, lying between Lakes Cham- 

 plain and Ontario. Upon this formation along 

 its whole contour rest the Lower Silurian de- 

 posits, the base of which, in the district more 

 immediately requiring description, makes an 

 elbow at the division-line between the counties 

 of Franklin and Clinton, in New York, not far 

 from the northern limit of the State, where the 

 deposits turn from the valley of the St. Law- 

 rence to that of Lake Champlain, the dip on 

 one side of the turn being to the north-west, 

 and on the other to the east. In the Canadian 

 distribution of the same deposits, after following 

 the valley of the St. Lawrence from Cape Tour- 

 ment to St. Jerome, with a south-easterly dip, 

 they turn to that of the Ottawa with an east of 

 south dip, forming a less acute elbow than the 

 former, with a contrary bend. These two elbows 

 are directly opposite to one another, and the 

 distance between them, from the gneiss on the 

 one side to the gneiss on the other, is about 

 fifty-eight miles, and, as might be anticipated 

 from the arrangement, a flat saddle-shaped anti- 

 clinal form (the dip being everywhere very small) 

 extends between them ; it brings to the surface 

 a long belt of the Potsdam Sandstone, which 

 runs upon it for forty miles, until meeting with 

 a protruding mass of gneiss in Mont Calvaire, 

 which it surrounds. This belt is flanked on 

 either hand by the Calciferous Sandstone and 

 Trenton Limestone, the latter containing abun- 

 dance of characteristic fossils, such as Chcetites 

 petropolitanus, Leptcena sericea, L. deltoidea 

 or euglypha, Orthis testudinaria, Spirifer lynx, 

 Calymene senaria. The beds in which the track 



VOL. VII. PART I. 



1 



