Ch. XVI.] 



I5Y RIVER ICE. 



3 r> 5 



dammed up waters and drift-ice. Thus propelled, it not only 

 forces along boulders, but breaks off from cliffs, which border 



the rivers, huge pieces of projecting rock. 



masonry 



means 

 3 year 



1836, supported a wooden bridge on the St. Maurice, m 

 falls into the St. Lawrence, near the town of Trois Eivieres, 

 lat. 46° 20', were thrown down, and conveyed by the ice into 

 the main river ; and instances have occurred at Montreal of 

 wharfs and stone buildings, from 30 to 50 feet square, having 



manner. We learn from 



mark 



* 



secure vessels hauled on shore for the winter, must be cut out 

 of the ice on the approach of spring, or they would be carried 

 away. In 1834, the Gulnare's bower-anchor, weighing half 

 a ton, was transported some yards by the ice, and so firmly 

 was it fixed, that the force of the moving ice broke a chain- 

 cable suited for a 10 -gun brig, and which had rode the 

 Gulnare during the heaviest gales in the gulf. Had not this 

 anchor been cut out of the ice, it would have been carried 

 into deep water and lost."* 



The scene represented in the annexed plate (PL IV.), from 

 a drawing by Lieutenant Bowen, B,.N., will enable the reader 

 to comprehend the incessant changes which the transport of 

 boulders produces annually on the low islands, shores, and 

 bed of the St. Lawrence above Quebec. The fundamental 

 rocks at Eichelieu Rapid, situated in lat. 46° 1ST., are lime- 

 stone and slate, which are seen at low water to be covered 

 with boulders of granite. These boulders owe their spheroidal 

 form chiefly to weathering, or the action of frost, which 

 causes the surface to exfoliate in concentric plates, so that 

 all the more prominent angles are removed. At the point a is 

 a cavity in the mud or sand of the beach, now filled with 

 water, which was occupied during the preceding winter(1835) 

 by the hugh erratic b, a mass of granite, 70 tons' weight, 

 found in the spring following (1836) at the distance of several 



from 



Many small 



on the river, such as c d, which afford still more striking 

 proofs of the carrying and propelling power of ice. These 



* 



* Capt. Bayfield, Geol. Soc. Proceedings, vol. ii. p. 223. 



