90) REPORTS ON THE STATE OF SCIENCE.—19]12. 
decrease is very slow and the curve tends to become asymptotic to the 
axis representing distance. Professor H. H. Turner very kindly ex- 
amined these curves, together with the observations on which they are 
founded, with the result that two of them were brought more closely in 
conformity with the remaining four. 
At the present time this investigation is, with additional material, 
receiving careful attention from Professor Turner. 
IV. Direction of Earthquake Motion, 
Between 1881 and 1882, partly in conjunction with the late 
Professor T. Gray, I carried out an extensive series of experiments on 
earth-vibrations produced by firing dynamite or some other explosive 
in boreholes of varying depth. The resulting movements were recorded 
by seismographs. One result repeatedly shown indicated that the first 
movement was invariably in the direction of the origin of the explo- 
sion.* 
An observation corresponding to this has been shown by Prince 
Galitzin to accompany teleseismic motion, and when it is pronounced 
it furnishes the azimuth of the epifocal district. To determine 
whether the mazimum movements of teleseisms showed any relation- 
ship to the direction in which they had been propagated I examined 
forty-two seismograms of North-South and East-West .motion es 
recorded at Shide. In the following table I give the number of a seis- 
mogram as entered in the Shide Register, published in the British 
Association circulars, its date, the latitude and longitude of origin of 
the disturbance to which it refers, the azimuth of this origin from Shide, 
and the azimuth as calculated from the North-South and East-West 
amplitudes. Each of these latter may be read as so many degrees east 
or a similar number degrees west of North. 
th of | Azimuth as 
Register No. | Date | Position of Origin | Origin | calonlated 
: bei! i? | 8 
1901 | 
496 | May 25 165 E. 12 N. N.20E. | N.30E, 
565 Dec. 14 121 E. 14N. N.57E. | N. 608. 
BTL) eDeew Sl 173 W. 41 N. N.15W. | N.11W. 
1903 | 
705 | Apr. 29 143 W. 43 8. N. 55 W. N. 54 W. 
| 1904 | 
820 Mar. 1 | 178 W. 128. N. 20 W. N. 25 W. 
838 Apr. 12 175 W. 44 N. N. 8 E. N. 12 E. 
847. | May 1. | 130K. 2N. N. 22 E. N. 30 E. 
860 | June 25 160 E. 53 N. N. 11 E. N. 17 E. 
s6é3. | June27 | 160K. 53 N. N. 11 E. N. 17 E. 
872 | July 24 1600 EF. 53N. | NIE. N. 25 E. 
877 | Aug. 8 179 E. 42 8. N. 5E. N. 13 E. 
884 | Aug. 24 135 E. 32 N. N. 42 E. N. 47 E. 
885 | Aug.27 | 141 W. 67N. N. 18 W. N. 20 W. 
| 886 | Aug. 30 | 101 E. 30N. N. 62 E. N. 57 E. 
889 Sept. 11 | 106E. 23N. N. 65 E. N. 65 E. 
924 Dec. 2 | 132K. 10N. N. 55 E N. 62 E. 
1 See Phil. Trans. R.S. snene iii., 1882, p. 871; Trans. Seis. Soc., vol. viii., 
1885, pp. 1-82; Brit. Assoc. ’ Reports, 1885, pp. 363, 364. 
