226 REPORTS ON THE STATE OF SCIENCE, ETC. 
town on the island. Mr. F. A. Perret, the American vulcanologist, has 
been consulted and has equipped a small research station. ‘These occur- 
rences have emphasised the need for more seismological stations in the 
West Indies. 
Microseisms—T wo papers on microseisms by A. W. Lee have been 
published during the year. At Kew Observatory, as previously at Eskdale- 
muir, the amplitude and period of the microseisms recorded by the North 
component seismograph have been measured four times a day. Mr. Lee 
made similar measurements of the microseisms recorded by the East and 
Vertical component seismographs during the year 1932. It was found that 
on the average the amplitudes of the three components were equal. As a 
result of this investigation it was decided that the vertical movements 
should be measured and published as from the beginning of 1935. 
In the other paper Lee has developed a method of determining the 
direction from which microseismic waves approach an observatory. ‘The 
successful application of this method provides a verification of the hypo- 
thesis that these waves are of the Rayleigh type, the movement of the 
ground being such that the earth particles move round ellipses or circles in 
a vertical plane ; the motion is retrograde, being opposite to that of a point 
on a wheel rolling along the ground in the direction of propagation of the 
wave. It is found that the microseismic waves generally approach England 
from N.W. and are associated with storms in the Atlantic. 
THE INTERNATIONAL SEISMOLOGICAL SUMMARY. 
A Note by Mr. f. S. Hughes. 
The International Seismological Summary for 1930 has been completely 
distributed, and the first quarter of 1931 is in the Press. The year promises 
to be an unusually heavy one, partly on account of increase in the number of 
stations, and partly by increased seismic activity in the early months. The 
Hawke Bay-New Zealand earthquake of 1931 (Feb. 2) is followed by 
numerous aftershocks, but owing to the uncertainty of the times from several 
of the New Zealand recording stations, only the few largest are sufficiently 
recorded for the purpose of the Summary. Other records from New Zea- 
land definitely attributed to aftershocks have been tabulated in full as far 
as the end of February. 
The new tables of Jeffreys and Bullen have now been in use for over 
a year, and the experience gained of them fulfils the hopes entertained of 
a more even fit of observation with theory along the whole scale of epicentral 
distance (as far as 100°). In particular, the few well-recorded earthquakes, 
for which nearly all the observational material was obtained within 20° of 
the epicentre, can now be determined with great accuracy. As stated in 
the Introduction to the I.S.S. for 1930, the P phase carries most weight 
in analysing the observational material and, as a result, the S phase recorded 
at distances where it is not usually confused with any other phase, sometimes 
shows systematic errors not easily explained, and much in excess of the 
probable error of the time curve. On 1931 January 15d. and 16d. two earth- 
quakes occurred at epicentre 16°4° N. 96:3° W., but, whereas for the earlier 
shock the residuals are nicely balanced both in azimuth and as between P 
and S, for the latter, although the P is equally good, the S is systematically 
late by several seconds. This effect is opposite to that where S is read too 
early and a suitably increased T, would make residuals resemble those 
associated with a shock of slight focal depth. This phenomenon is attri- 
