10 ART. 9. S. KUSAKABE. 



The relation between the modulus of elasticity and the 

 amount of bending is given by the well known formula. 



X1j = ï pi 



ab a 

 where a and b are the breadth and thickness of the specimen, 

 while I is the distance between the corresponding fulcrums. 



EXPERIMENTAL RESULTS. 



The last investigation with regard to the modulus of rigidity 

 proved a great deviation from Hooke's law even in the case of 

 the least strain. Preliminary experiments showed it to be the 

 same also in the case of bending. Looking at the curve in Fig. 

 8, we see that there is a tendency on the part of the rock to 

 persist in any strained state which it may have acquired, especially 

 when the variation of the stress changes its sign. The curve is 

 closed and it is also of simple and regular form, though its path 

 during the increase of stress differs entirely from that during the 

 decrease. All rocks, so far as the author has investigated, have 

 this jDroperty in common, though they differ in the character of 

 the curves and in other minute details. 



It may be suspected that, as the resisting mass increases 

 with the total mass to be moved, this may have some in- 

 fluence upon the hysteresis curve. The comparison of the results 

 of four successive experiments, in which the resisting mass was 

 1000, 1300, 1600 and 1900 grams respectively, while all other 

 conditions remained the same throughout, showed that the influence 

 of the resisting mass might be safely neglected. 



There is one important fact which deserves to be mentioned 

 here. Altliough the hysteresis curve is of a definite form and 



