ON SEISMOLOGICAL INVESTIGATIONS. 245 



Copies of the circular were supplied to the members of our national committee on 

 Geodesy and Geophysics, and a sympathetic motion in support was passed. The 

 printing account up to and including the cost of the I.S. Summary for 1925 was given 

 in the last Report. The cost of printing in 1926 was much greater than its predecessors, 

 amounting to £382 as against £280 in 1925. The increase may be partly due to 

 temporary causes, but it would be unwise to make this assumption, in the present 

 state of our knowledge ; certainly it is in part due to the increase in the number of 

 observing stations which send their readings for collation ; and as the science pro- 

 gresses it will almost certainly be necessary to give details additional to those at 

 present given, which may be regarded as an irreducible minimum. Hence the printing 

 bill is not likely to become smaller. In response to an appeal in May 1929, the Royal 

 Society kindly made an additional grant of £150 to meet the deficit on the printing 

 account, with an intimation that it must be the last. They have contributed £525 

 in all during the last four or five years. 



The work of preparing the Summary for printing has hitherto not received any 

 aid from the funds allotted to the Seismology Section ; it has been subsidised by the 

 British Association, by the Department of Scientific and Industrial Research, by the 

 Royal Society, by the University of Oxford, and especially by Dr. Crombie, without 

 whose constant generosity the work must have come to an end long ago. 



Bulletins and Tables. 



The International Seismological Summary for 1926 has been printed and circulated, 

 and the first quarter of 1927, which will be the tenth year of the Summary(1918-1927), 

 is in the press. The work of preparing and printing the Summary has increased so 

 steadily as to balance any gain due to experience and to ihe use of computations for 

 previous epicentres, so that the idea of revising years previous to 1918 (especially 

 1916 to 1912, for which much new material has come to hand since the pubhcation 

 of the partial results in the Bulletins of this Committee), long contemplated, has not 

 yet been carried into effect. Nor has it been possible to do much in the way of 

 discussion of results, though the following may be mentioned : — 



(a) The shock of 1926 Oct. 3d. 19h. at 50°-5 S. 161°-0 E. provided a large number 

 of observations of [P], the longitudinal wave which goes right through the earth's 

 liquid nucleus and arrives at stations near the anticentre, many of which in this -^ase 

 were in Europe. The results showed that the empirical formula adopted in March 

 1922 is substantially correct except for stations not very far from the epicentre 

 (say A = 120°) where it seems to require correction. But if so, Gutenberg's values, 

 calculated from theory, would also require correction. Our empirical formula (using 

 a simple parabolic curve) agrees well with Gutenberg, except that his theory introduces 

 a slight discontinuity at A = 146°. 



(6) The same shock (1926 Oct. 3d.) provided a number of L observations, which 

 were mainly suited by the velocity 1° in 0-405 min., or 4-57 km. /sec, though they 

 were apparently divisible ir:;o several groups with different starting-points, and 

 some of them were not L waves at all. The details are given in the Sjimtnary for 

 1926, October-December. But on trying this speed for other shocks it was found 

 quite unsuitable, except in a few cases. For the great majority the speed is represented 

 by 1° in 0-477 min., or 3-88 km. /sees. This seems to suggest that in the majority of 

 cases the waves noted as L by observers are Rayleigh waves, while in some special 

 cases they are chiefly Love waves. The details are not yet quite ready for publication. 



(c) A number of cases of Gutenberg's S PcS, denoted by [S], and of Gutenberg's 

 ScPcPcS, denoted for convenience by S, have been noted in'the Summary for certain 

 earthquakes, and found to give residuals from his curves which are satisfactorily small. 



Deep Focus. 



The paper sent to Mr. Wadati has now appeared in the Tokio Geophysical Magazine 

 and was also printed in the I.S. Summary, while its fate was still in doubt. The 

 cases of deep focus were collected by Miss Bellamy in card catalogue form, and also 

 plotted on a map, when it was found that they had a definite local distribution. A 

 rough diagram of this arrangement was prepared for the I.S. Summary for 1927, 

 J.F.M., and is reproduced with this report. The epicentres are confined to a com- 

 paratively small portion of the earth's surface and arranged approximately in an oval 



