August iy, 1911] 



NATURE 



221 



directly or indirectly to the inhabitants of India, and 

 shows how much is gained by effective organisation 

 and cooperation. We could wish that similar co- 

 operation of scientific and technical work existed in all 

 regions, as it already does in some, since it not only 

 favours efficiency and economy, but also provides a 

 useful summary of results obtained, which are often 

 hidden in the administrative detail and statistics of an 

 annual progress report, though they may appear 

 subsequently in a detailed publication. 



EARTHQUAKE STUDIES. 



"THE last two bulletins of the Imperial Earthquake 



-*■ Investigation Committee (vol. iv. , No. 2, and 



vol. v., No. 1) are each from the pen of Dr. F. Omori. 



The second memoir deals with the eruption of 

 Mount Usu, in Vezo. This began at the end of July, 

 19 10, and resulted, amongst other things, in the 

 formation of about fifty craterlets parallel to a lake 

 shore. The highest of these was about 700 feet. As 

 these were formed, not only did the shore of the lake 

 rise, but there was a rapid upheaval of ground to 

 form a new mountain. This approximately reached 

 to the same height as that of the craterlets, when its 

 growth suddenly ceased. A curve of barometric pres- 

 sure and another of earthquake frequency in the 

 vicinity of the mountain, but prior to its eruption, 

 shows that premonitory shocks began when atmo- 

 spheric pressure was least, and that the first volcanic 

 explosion occurred when it was at a maximum. The 

 frequency of volcanic after-shocks does not appear to 



■^■■■■^^■■■■HHHi 



Fie. 1.— The Craterlets 



the right side is the 



Group opposite the New Mountain, se 

 Faji-Yama." To the tight-hand side 



The first relates to the vibrations of railway-bridge 

 piers and trusses. The period of transverse and longi- 

 tudinal vibrations of piers S2 feet in height was found 

 to be from o'2 to o'4 second. As this is much shorter 



have followed that which is usually followed by the 

 after-shocks of a large earthquake. Dr. Omori points 

 out that there are many instances in Japan where 

 volcanic eruptions have been preceded by numerous 



Fig. = — General v 



at the left-hand side 

 ght side of the figure. 



than that of a destructive earthquake which is from 

 1 to i'5 seconds, the inference is that in a great earth- 

 quake these piers would be expected to fracture at 

 their base. 



NO. 2 1 8l, VOL. 87] 



earthquake shocks and "jinaris" (earth-sounds). 

 Whenever this is the case, tromometer and seismo- 

 graph observations should give warning of an ap- 

 proaching outburst. J. Milne. 



