DE VE L OP ME NT OF S BISMOL O G V IN J A PA N 293 



Matuzawa^^^ also discussed the criterion for the existence of 

 gravitational waves in the superficial soil layer of the crust which he 

 treats as a highly viscous fluid. He tabulates the lower limits of 

 wave-length for which the periodic motions are possible for different 

 values of viscosity. From his result, he concludes that the furrow-like 

 corrugation formed on the surface of the soil in destructive earthquakes 

 is not due to any wave motion, as was sometimes believed, but to 

 aperiodic deformations caused by solitary impulses. He also considers 

 the vibration of a soil layer to be expected when the underlying rock 

 layer is subjected to a wave motion. The result of calculation is 

 applied for the explanation of the relative intensities of shocks in 

 different quarters of Tokyo on the occasion of the recent great earth- 

 quake. N. Nasu^^^ had investigated the relative intensities for different 

 points in Tokyo from the instrumental observations of the after-shocks 

 of the great earthquake as the functions of the periods erf vibration. 

 The result obtained by the latter may partly be explained by JVlatu- 

 zawa's result of calculation. Moreover, Matuzawa remarks that the 

 pulsatory motions may partly be attributed to the effect of the super- 

 ficial soil layer. 



Lastly, we may cite here some of the theories regarding the causes 

 of earthquakes which were propoundtd in connexion with the recent 

 great earthquake. Among the others, the most original is perhaps 

 that proposed by S. Fujiwhara.'"^ He has been for some years studying 

 the significance of the occurrence of some characteristic torsional or 

 vortical forms in the arrangements of mountain ranges, chains of 

 islands, etc, together with the distribution of cracks and creases 

 accompanying these forms. On the other hand, he carried out a series 

 of very simple but ingenious experiments with different kinds of [lasty 

 masses. He accepts the hypothesis of the continental drift alter 

 Wegener and Joly, but lays his stress on the effect of the rotation of 

 different moving parts and of the shearing thereby produced. In one 

 of his recent papers,^"*^ he points out a peculiar regularity in the 

 arrangement of volcanoes in Japan, which luay be accounted for in 

 connexion with the echelon cracks obtained by his experiments. The 



(1) Jap. J. Astr. Geophys., 3 (1925), 162. 



(2) IIo., lOOA (1925). 



(3) J.M.S., 43 (1924s 6; Jap. J. Astr. Geophys, 3 (1925), 103; Nagaoka Anni- 

 versary Volume, 3oo. 



(4) Geogr. Kev., 1 (1^25), 735. 



