﻿1851.] 



BIGSBY ON CANADIAN ERRATICS. 



217 



Silurian System, according to Mr. Logan, who had the kindness to 

 examine some of my specimens. 



On the west mainland, a little north of Monument Bay, there is an 

 island, which is almost connected to the main by an immense depot 

 of primitive boulders, principally foreign to the lakes ; while its eastern 

 end is in deep water. 



The points to be noticed in the Lake of the Woods are — the abun- 

 dance and universality of primitive travelled blocks, — their northern 

 origin, — the total absence of calcareous erratics on the north, — and 

 the large sand-beds in the southern part of the lake. 



There may be striae and scorings, but they did not attract my 

 attention here as they did in the Canadas. 



River and Lake La Flute. — We now proceed to the beautiful river 

 La Pluie. This river flows westerly for eighty-five miles out of Lake 

 La Pluie, and pours into the Lake of the Woods near long. 95° W. 



It passes through a level or rather undulating country, with banks 

 varying from 5 to 50 feet in height, with terraces here and there, 

 although rarely : these, however, the luxuriant forests only permit to 

 be seen for short distances. 



Throughout the whole length of the river La Pluie, its banks ex- 

 pose a grey clayey and loamy soil, full of small angular fragments of 

 the yellow limestone of the Lake of the Woods, intermixed occasion- 

 ally with round lumps of gneiss, from the size of the fist to that of 

 the head. I saw no marks of stratification, nor any marine or fresh- 

 water shells. 



The limestone was sometimes, as just below Fort La Pluie, so plen- 

 tiful and fine as to form a conglomerate rock with a calcareous paste 

 and nodules of primitive rocks ; while close to and below the river 

 Boudet the limestone masses have concreted into a hard breccia, 

 without the primitive nodules. There are not many primitive boulders 

 lying exposed on the river La Pluie ; but they are in great numbers 

 at the Long Sault and Manitou Rapids, — obstructed points in the 

 river, where sand, gravel, drift-wood, and large boulders of trap, &c. 

 have greatly accumulated. Along the Manitou Rapids and elsewhere 

 we see a good deal of pure clay in the banks. 



It may be safely concluded from reasons not necessary to be men- 

 tioned here, that the Sandhill portion of the Lake of the Woods and 

 a considerable region around the river La Pluie form one great lime- 

 stone basin. By far the larger part of the superincumbent detritus 

 is native, while the foreign comes from the north, — not from the 

 south, with whose rocks I am tolerably well acquainted. 



Rainy Lake, 1 160 feet above the level of the sea, 300 miles round, 

 but of a most irregular shape, next succeeds on our route southwards 

 towards Lake Superior. 



For a few miles round the mouth of the river La Pluie we have 

 the yellow calcareous debris, before spoken of, in large quantities, — 

 one mass I saw weighed more than a ton ; but on entering further 

 into the lake we see no more of it. 



I observed no terraces in Lake La Pluie ; the general level being 



VOL. VII. PART I. Q, 



