[barnes-hayward- EXPANSIVE FORCE OF ICE 43 



MCLEOD] 



rid of ice. Some water was pumped out of the beds under the ice and 

 soon after the ice thawed along the concrete walls and pillars, and 

 settled down on the water again without breaking or getting jammed. 

 A steam boiler was erected and live steam blown into the water under 

 the ice. This proved very effective locally, but not enough circulation 

 could be set up to melt a wide area. 



Theory of Ice Cracks. 



The forces set up in a large sheet of ice when the changes of 

 temperature occur are very great. They are also unequally distributed 



CONTRACTION 



«C£ """~"~ V ~~ """SHEET 



wate k at crc 33°f. 



EXPANSIO |\J 



WATER AT 0°C 3£°F 



Figure 6. 



throughout the ice thickness, and thereby cause the ice to bend 

 readily. It has been concluded by many observers that a large ice 

 sheet will buckle and bend before the ultimate crushing strength of 

 the ice is reached. This we believe to be true, for the strains set up 

 in the ice sheet all tend to assist this bending. Let us consider the 

 contraction and expansion of an ice sheet represented in Fig. 6. In 

 the upper block we suppose the upper surface subject to a cooling 

 atmosphere below the freezing point. The under surface of the ice 

 being in constant contact with the water cannot ever differ by more 



