ICE PHENOMENA. 415 



This property of expansion and contraction of ice aids in fracturing 

 and reducing the floating and gigantic iceberg ; and Dr. Kane tells 

 us, that but for changes of ice at temperatures /«r helow the freezing 

 point, causing pressure, collapse, fracture and disruption, the short 

 Arctic summer would fail to open the Arctic Seas. I may add, that 

 the ignorance, or want of a proper appreciation, of the properties of 

 ice, evinced in the construction of numerous wharves, piers, and 

 bridges on the inland lakes and rivers of Canada and the northern 

 States, has proved a source of infinite annoyance and of immense 

 expense. 



The Cobourg and Peterborough Railway bridge across Rice Lake 

 supplies a remarkable instance, from observations of the effects of ice 

 on which some valuable practical conclusions may be deduced. Tim- 

 ber being plentiful along the shores of this lake, a cheap and substan- 

 tial form of pile and truss bridge was constructed. 



This bridge on more southern waters would doubtless have been 

 considered a most suitable structure, but owing to the violent and 

 almost irresistible force of ice, while expanding, a considerable por- 

 tion of this structure now presents the appearance of a complete 

 wreck. Having, as Engineer of the Cobourg and Peterborough Rail- 

 way, had two winters' experience of ice phenomena on Rice Lake, and 

 having carefully noticed the peculiar circumstances attending the 

 various movements of the ice, I submit my observations and remarks, 

 hoping that from them a somewhat satisfactory and perhaps correct 

 theory may be deduced. 



In the first place, it is well to know, that the violent movement of 

 the ice on Rice Lake is that of contraction and expansion, caused 

 entirely by change of temperature. The lake generally " takes " with 

 ice during the month of December at a pretty high water level, which 

 level the dam across the outlet preserves until spring. Currents, 

 therefore, cannot be said (as in the case of rivers) to influence the 

 movements of the ice. Neither have we on Rice Lake those other 

 various causes, such as difPering temperatures of ice and sea water, 

 currents, or wave action, which produce the disruptions of Arctic ice. 

 It is observed on Rice Lake that the action of the mid-day sun will 

 set the glare ice immediately in motion. Warm winds, snow storms, 

 and rains, do likewise produce the same efi'ect, when the ice is glare 

 and free from water or snow. This motion is generally quite percep- 

 tible ; it is not shrinkage, or contraction, but on the contrary is a 



