Canon Moseley on the Mechanical Properties of Ice. 7 



The Shearing of Ice. 



Two blocks of hard wood, each 3 inches in thickness, had 

 their surfaces carefully fitted to one another, and the one was 

 adjusted so as to slide on the other by means of guides. The 

 two were then pierced through in a direction perpendicular to their 

 planes of contact by a cylindrical hole 1-J inch in diameter. The 

 apparatus (fig. 8) was used in a vertical position, one of the blocks 

 being screwed to a carpenter's bench near the edge, the other 

 block overhanging the edge. From this second moveable block 

 a scale-pan was suspended by a strong cord. The two blocks 

 being then brought so that the cylindrical hole in the one cor- 

 responded with that in the other, a cylinder of ice turned in the 

 lathe to a diameter of l^inch was inserted through the two, and 

 weights were added to the scale-pan until the cylinder of ice 

 began to be sheared across. The process of shearing was slow, 

 notwithstanding that it was accelerated by the melting of the ice 

 by reason of the heat conducted from the apparatus, and of the 

 pressure sustained at the upper and lower surfaces of the cylin- 

 der, by which its temperature of congelation there was lowered. 

 After about thirty minutes the weights were removed, and the 

 cylinder, now sheared partly across (fig. 9), was taken out of the 

 apparatus. There was not the least appearance of separation in the 

 plane a b, over which a surface of ice had been continually shear- 

 ing. The new surfaces made to slide into contact had entered 

 into precisely the same relations with one another as they had 

 to the surfaces with which they were before in contact, and the 

 ice was continuous. 



Thirteen such experiments were made. Their results are re- 

 corded in the following Table*. The last six were made, not 

 with cylinders turned out of solid ice, but formed by regelation — 

 by hammering with a mallet and a solid rammer broken pieces of 

 ice into the cylindrical holes of the apparatus when brought 

 together so as to form one hollow cylinder. 



* The unit of shear cannot be determined by experiment with absolute 

 accuracy, except by taking into account the observed time of shearing. In 

 the case of a cylinder this determination is difficult ; but in the case of a 

 prism having a rectangular section it is comparatively easy. If a and b 

 be the sides of such a section in feet, W the shearing-weight in lbs., 

 /* the unit of shear in lbs. per square foot, and t the time, in seconds, of 

 shearing through the distance x, 



where a, b, g are known, and W, t, x are determined by the experiment ; 

 the equation determines therefore /x. 



