﻿1851.] 



BIGSBY ON CANADIAN ERRATICS. 



233 



ridges of naked boulders, or heaps of sand ranging along shore. They 

 are particularly well-marked ten miles west of Presqu'isle. 



From the Quinte Portage to Kingston, seventy-five miles, princi- 

 pally along the winding Bay of Quinte, gravel-banks prevail on the 

 north mainland, which are full of rounded blocks of granite, green- 

 stone, and gneiss. This is well seen in the Bay of Quinte, twenty- 

 seven miles from Kingston, and at Adolphus Town. 



I have visited the country in the rear of the Bay of Quinte for thirty 

 or forty miles northwards. It contains the Trent and Moira Rivers, 

 together with numerous lakes. Its erratics are in vast numbers, 

 distributed equably. They are of all the usual sizes, and are gneiss, 

 syenite, &c, derived from the north and north-east. In uncleared 

 parts we meet with naked platforms of limestone, many acres in ex- 

 tent, on which we find these foreign blocks reposing. 



Although I desire this Communication to appear mainly as a col- 

 lection of facts, perhaps I may be permitted to make the following 

 few observations ; — first, on the loose detritus, small and large ; 

 and secondly, upon the imbedded detritus. 



We have seen that the loose detritus of the Great Lakes may be 

 arranged into three kinds : — 

 L The distant erratics. 



2. The near or lake erratics. 



3. The native debris. 



The condition and relations of the first kind are everywhere so 

 similar, and their presence or range so extensive, that the producing 

 agency must have been proportionately extensive, and probably of 

 long continuance, — loaded ice-bergs, travelling from the north, — or 

 an earthquake sea-wave with subsequent submergence. 



The general courses of the boulders, &c, traced from their 

 parent rocks, may be seen on the Map, PL XIV. ; on which the courses 

 of the scratches and boulders, as laid down by Prof. Hitchcock, and 

 the tracks of the erratics observed by myself, are respectively shown. 

 In my operations, I have been much aided by the occurrence of 

 strongly characterized boulders, and by observations made during 

 previous journeys that extended 400 miles to the north of Lake Supe- 

 rior, 150 miles north of Lake Huron, and 200 miles north of Lake 

 Ontario. 



The prevailing direction of the first, or distant class of erratics 

 throughout the valley of the St. Lawrence, is southerly as far as is 

 known. In Lake Huron many boulders have travelled S.S.E. In 

 Lake Ontario, on the river St. Lawrence, both above and below 

 Quebec, they have been carried W.S.W. contrary to the present 

 current of that river. 



The exact line of march cannot always be determined, from the 

 great extent of the formations furnishing the boulders. I refer to 

 gneiss, syenite, marble, &c. The white marble, for instance, occupies, 

 on the north of Lake Ontario, two degrees of latitude and six of west 

 longitude. 



VOL. VII. PART I. R 



