6 Canon Moseley on the Mechanical Properties of Ice, 



Experiments on the Crushing of Ice, August 26, 1869. 



A wooden frame was constructed (fig. 7), having fixed to its 

 base two vertical iron rods, on which traversed a strong wooden 

 platform intended to carry the weights necessary to crush a cy- 

 linder of ice placed vertically beneath the platform. The first 

 experiment was made with a cylinder 1J inch in diameter and 

 2 T 1 g inches long. It bore without crushing 578 lbs. for forty 

 minutes, during which time its diameter diminished by thawing 

 to If inch. Planes of cleavage at right angles to the axis formed 

 themselves as the loading went on, all down the cylinder, and 

 also longitudinal planes, some of which passed through the axis, 

 and others were parallel to it. This shorter cylinder was then re- 

 placed by one of the same diameter (1J inch), but 6 inches long. 

 It showed signs of failure, first, by a slight bending in the middle, 

 then by the formation of a plane of shearing at an inclination of 

 23° to the horizon at its middle point, round the edges of which 

 plane it bulged out into a sort of lip (see fig. 10) . iUong this 

 plane it slowly sheared with a pressure of 545 lbs. While it 

 was in the act of shearing, planes of cleavage formed themselves 

 parallel to the axis; and along them it finally split up. Knowing 

 the inclination (c) of the plane of shearing, the radius (r) of the 

 cylinder, the incumbent pressure P, and the limiting angle (<£) 

 of the resistance of friction, the unit of shear (/ul) is determined 

 by the equation 



_ Psin (i—<j>) cost 



p= 



irr 2, cos $ 



from this formula (assuming <f> to be 2°) we obtain 



fi= 101-8 lbs. 



This will be found not to differ much from the unit of shear de- 

 termined by the direct shearing of ice. The crushing-pressure 

 (545 lbs. upon a cylinder 1^ inch in diameter) is equivalent to 

 308*4 lbs. per square inch. Assuming ice to be of the same 

 specific gravity as water, a strip 1 square inch in section and 

 710 feet high would have this weight. Supposing a great num- 

 ber of such strips to be placed together vertically so as to form 

 a glacier, that glacier (710 feet deep) would only just, by its 

 weight, crush itself upon its base. 



As there is no glacier alleged to have so great a depth as 

 710 feet, this fact is an answer to that theory which attributes 

 the descent of a glacier to the crushing of the ice of its base by 

 the incumbent weight. 



