1854.] BIGSBY — GEOLOGY OF RAINY LAKE. 215 



This may be particularly noted in passing into Fieshwick Bay from 

 Rushen Church, and in the terrace extending between Port St. Mary 

 and Port Erin. Another argument in favour of this hypothesis is 

 found in the entire absence of any water-worn caves at any great 

 height above the present level of the sea. 



I believe that the re-elevation was of such an extent as to lay dry 

 the whole area of the Irish sea, and thus to connect the Isle of Man 

 with the surrounding countries, and these countries with each other. 



Over the plain, so formed, the Megaceros Hibernicus immigrated 

 into these regions, as we find its remains buried in freshwater deposits 

 which were formed in depressions of the drift-gravel terrace. 



There was, however, a subsequent period of subsidence to a partial 

 extent, and then a stationary period, which is indicated both by the 

 great excavations in the drift-gravel made by the sea at a higher 

 level than at present, and also by the presence of deep water-worn 

 caves at the height of about 12 feet above the present sea-level. 



2. On the Geology of Rainy Lake, South Hudson Bay. 

 By Dr. J. J. Bigsby, F.G.S., &c. 



[Plate X.] 



Geographical position, &c. — Rainy Lake, or Lake Lapluie, is 

 placed on the great commercial route from Canada to Prince Rupert's 

 Land and the north-west fur countries. 



It is 225 miles west of Lake Superior, and 85 miles south-east of 

 the Lake of the Woods*, from the head of Rainy River; but at 

 Nahcatchewonan River it is only 37 miles distant from that lake. 



This lake, 50 miles long by 38| miles broad, is 294 miles round 

 by canoe-route. Its form, like that of most bodies of water resting 

 on plutonic rocks, is extremely irregular, being in three great troughs 

 (with deep lateral indents), one of these running easterly, and the 

 other two in a northerly direction. See Map, Plate X. 



The immediate shores are usually low, rarely cliffs or earthy 

 banks ; but they rise in shaj^eless masses of rock, often naked, with 

 broad marshy intervals ; or in ridges, which become hills 300-500 

 feet high at distances from the lake varying from half a mile to 

 four miles. 



The low grounds are well covered vdth small trees, such as are 

 common in these regions, and the higher abound in Vaccinece and 

 other useful fruit-bearing bushes. 



Rainy Lake is 1160 feet above the level of the sea, according to 

 Capt. Lefroy. Its water is pure and clear, but seldom deep, and 

 the spring-freshets rise to the height of from 3 to 5 feet. Its 

 magnetic variation is 10°-12° E. 



"We counted 516 islands; but there are more. They are mostly 

 small and marshy ; and never exceed four miles in length. 



* Quart. Journ. Geol. Soc. vol. viii. p. 400, and pi. xxii. 



