292 



ON THE HYDROLOGY OF THE BASIN 



been done for about $1.10; and in Western Canada, $2.00. In all cases, the work was 

 in deep water; and in the case of Quebec, it varied from twenty-eight to thirty-eight feet 



in height. 



The attention of the writer has been drawn to one of the effects of ice, which has not 

 yet been mentioned, and that consisting in the expansion of large unbroken fields of ice, 

 and which has produced the most serious injury to public works. 



The line of the Cobourg and Peterboro' Railroad crosses over Rice Lake about ten 

 miles north of Lake Ontario, by a bridge of nearly three miles in length. The lake is 

 about eighteen miles in length, and obtains its maximum width at the point of crossing, 

 and is about twelve feet deep. Early in the season, this lake becomes covered with ice, 

 which occasionally increases to a thickness of two feet. 



The bridge or viaduct, for about five-eighths of its length, consists of a scries of short 

 spans, of from twenty-five to thirty-five feet clearance, each resting upon blocks of crib- 

 work,' about fifteen feet scpiare. The remainder consists of larger spans, some of them 

 extending to even seventy feet opening. 



The effect of the expansion of ice has here been felt, and for a few years after its con- 

 struction the most serious injury was done to the structure. The cribwork in many cases 

 was turned on one side, the whole line moved out of range, and the railway itself was 

 rendered almost impassable. 



To obviate, or rather to mitigate this mischief, the engineer ploughed a groove through 

 the ice, on each side of the bridge: the result of which was, that in thus finding the line 

 of least resistance, the ice was broken up, and the pressure greatly reduced. The mis- 

 chief, however, could not be wholly repaired, and the company has been engaged for the 

 last four years in filling up the lake along the line, thus forming an embankment of earth. 



Cribwork is most extensively employed on all the canals, wharves, railways, and other 

 structures of the country. 



