﻿LAKE WINIPEG. 65 



limestone cliffs. Under the action of frost, the 

 thin horizontal beds of this stone split up, crevices 

 are formed perpendicularly, large blocks are de- 

 tached, and the cliff is rapidly overthrown, soon 

 becoming masked by its own ruins. In a season 

 or two the slabs break into small fragments, which 

 are tossed up by the waves across the neck of the 

 bay into the form of narrow ridge-like beaches, 

 from twenty to thirty feet high. Mud and vege- 

 table matter gradually fill up the pieces of water 

 thus secluded ; a willow swamp is formed ; and 

 when the ground is somewhat consolidated, the 

 willows are replaced by a grove of aspens.* Near 

 the First and Second Rocky Points f, the various 

 stages of this process may be inspected, from the 

 rich alluvial flat covered with trees and bounded 

 by cliffs that once overhung the water, to the pond 

 recently cut off by a naked barrier of limestone, 

 pebbles, and slabs, discharging its spring floods 

 into the lake, by a narrow though rapid stream. 

 In some exposed places the pressure of the ice, or 

 power of the waves in heavy gales, has forced the 



* The fact of the formation of these detached ponds, marshes, 

 and alluvial flats points either to a gradual elevation of the dis- 

 trict, or to an enlargement of the outlet of the lake, producing 

 a subsidence of its waters. 



I The strata at these points contain many gigantic ortho- 

 ceratites, some of which have been described by Mr. Stokes in 

 the Geological Transactions. 



VOL. I. F 



