﻿1851.] 



BIGSBY ON CANADIAN ERRATICS. 



223 



to abut upon lofty hills. The boulders are arranged either con- 

 fusedly, horizontally, or in short interrupted lines at different angles 

 with the horizon. 



Before we leave Lake Superior, we may advert to the form of the 

 trappose islands of the north shore in the neighbourhood of the Peek 

 River. They are in very low, oblong ridges, rounded like woolsacks 

 or the backs of sheep (moutonnee), with very narrow intervals between 

 them growing bilberries. The surface of these ridges or mounds is 

 often glazed to the depth of half an inch, 



Fig. 1 represents one of these islands. It is 30 feet high. 



Fig. 1. — One of the low bare Greenstone Islands about the Peek, 

 Lake Superior. 



a. Mainland, consisting of Granite and Syenite, near the Greenstone Islands (6 miles off). 



b. Island of Greenstone, rounded and moutonnte. 



Lake Huron. — The rocks of Lake Huron, its contour, and its depth 

 being different from those of Lake Superior, we necessarily find the 

 nature and quantity of its detritus also to be extremely different. 



An idea of its shape can be best obtained by a glance at the Map, 

 PI. XIV. 



It is 1000 miles round ; and about the middle is sometimes 1000 feet 

 deep, being often shallow, however, along its northern division. It 

 is 594 feet* above the Atlantic ; and is all but bridged over length- 

 wise by a chain of large islands. 



The north shore of Lake Huron is mostly low and marshy ; sel- 

 dom showing cliffs overlooking deep waters, as in Lake Superior ; 

 and its hills (once or twice 700 feet high) approach the lake at a 

 small angle in successive ranges or lines ; and thus leave low inter- 

 vals between them, in which rivers may flow and detritus accumulate. 



Its eastern shore from Penetanguishene to Notawasaga Bay, having 

 Lake Simcoe (125 \ feet higher) in the rear on the east, rises insteps 

 to no great height, perhaps 300 feet, based on limestone ; these are 

 much covered by sand and erratics. 



From Notawasaga Bay to Cabot's Head the coast displays, first, 

 ranges of clay or sand-hills, and then a series of limestone cliffs. 



From Cabot's Head, or near it, to the river St. Clair, a distance 

 of 140 miles, the south-eastern shore is laid out chiefly in tall cliffs 

 of sand and clay ; but of which I know nothing, having never been 

 nearer than two miles from them. 



* The correct height of Lake Huron above the sea is 578 feet, according to 

 Mr. Logan. 



