6 ART. 1. — S. KUSAKABE : FREQUENCY OF 



acted ; (2) the residual surviving the couple after it has been 

 withdrawn increases with the increase of the time during which 

 the couple acted on the specimen ; (3) the residual diminishes 

 with the lapse of time and ultimately wholly disappears after an 

 infinite time, i.e. rocks from instant to instant recover from their 

 yielding to overstrain. 



In the case of flexure,* though it is not so enormous as in 

 the case of torsion, the phenomena of yielding and of recovery 

 are sufficiently great to be dealt with. To give one instance ; in 

 a piece of sandstone which was loaded with 3000 grams-weight, 

 the amount of bending was «=27.95 x 10~^ radians at the instant of 

 loading. The latter quantity, however, increased to « = 33.86x10"* 

 after 3§ hours and to « = 60.57 x 10""* after about sixteen hours. 

 Further increase of the flexure could be distinctly observed during, 

 about two weeks till at last the yielding, though it w^as still 

 steadily increasing, was much obliterated by the influence of the 

 temperature-change. 



After about two weeks, i.e. 20363 minutes, the specimen was 

 unloaded and the amount of residual bending was observed from 

 instant to instant. As in the case of torsion, it recovered gradually 

 and incessantly. The result of the experiment is given in the 

 following table. 



* For the melliod of lue.isurement and other details the reader is referred to tlx» 

 author's paperss : Puh. of the E. I. C. iu F. L. No. 17. Tokyo, and this journal, Vol. XX. 

 Art. 5). 1900. \\i abstract is also given iu Proc. of tiie Tokyo Physico-Matiiematical 

 Society, Vol. 11. No. 11. 



