626 MOTONORI MATSUYAMA 



knife-edges, thus preventing free movement. On account of this, the 

 result may not be much reHed upon and consequently the relative 

 ease of bending of the bars a and h is not determined. The other 

 observation stated above also failed to give any idea about this. 



As to the nature of deformation of ice comprising of an aggregate 

 of crystals, many authors have claimed that it depends upon the 

 behavior of a single crystal. It is stated that in a case of bending 

 of an ice bar consisting of several crystals, most of the bending had 

 taken place in one of the crystals lying with its crystal axis nearly 

 horizontal and approximately parallel to the length of the bar.^ 

 This is understood to mean that in such a case movement along 

 the gliding planes of an ice crystal parallel to its basal plane is more 

 effective than movements along the contact surfaces of adjacent 

 crystals. If this theory is applicable to the present case the third 

 bar in which the gliding planes were transverse to the long dimen- 

 sion should bend most easily. But quite to the contrary, bar of 

 orientation c, instead of bending most readily, suffered the least 

 bending of any of the three types of orientation. 



As to the mechanism of bending within the limit of perfect 

 elasticity it is generally understood by physicists that bending of 

 a bar is caused by shortening of the concave side and elongation 

 of the convex. When bending becomes larger than this, it is 

 difficult to solve the case as a simple mechanical problem. It is 

 probable in such a case that the portion near the point of appUca- 

 tion of force is subjected to bending, while the other parts are 

 elongated with some degree of sliding at the knife-edges. The 

 mechanism at the bending-point will depend upon the structure 

 of the material. If it is deformable more easily in one direction 

 than in another the problem becomes complicated. The resulting 

 deformation in such a case will be the combination of that effect 

 with the result of shortening and elongation phenomena. The 

 experimental fact above described that bars of type c bend less 

 easily than the others suggests that contact surfaces between 

 adjacent crystals play greater role than the so-called gliding planes 

 parallel to the basal plane. 



I R. S. Tarr and J. L. Rich, Zeits.f. Glets., Vol. VI (191 1), p. 236. 



