388 
MR. GEORGE W. WALKER ON 
means of examining this point by means of the vertical component. The following 
examples, taken from specimens published by Galitzin, illustrate the matter :— 
(1) Fig. 5. August 15, 1913. a = azimuth = 58° 37' N.E. A = 8540 km. 
Epicentre 27° N., 142° E. 
Second phase sharp in E. 
Movement South = 0. East = 7‘1 mm. Vertical = 2'0 mm. 
Thus along a we get 6T mm. _L to a 3'7 mm. So that H/V = 3'0, and from the 
curve, fig. 3, e = about 57° (or 73°). 
(2) Fig. 4. August 1, 1913. a = 38° 24' N.E. A = 7100 km. Epicentre 47° N., 
155° E. Second phase sharp in E. 
North = 3'0 mm. West = 23'0 mm. Vertical = 6‘0 mm. 
Therefore along a we get 11 ‘9 mm. _L to a 19’9 mm. Hence H/V = 2, or 
e about 60°. 
(3) July 26, 1913. a = 49° 26' N.W. A = 2490 km. Epicentre 67 0, 5 N., 
18‘6 W. 
Second phase sharp in E. 
South = 9'5 mm. West = ll'O mm. Vertical = 2'0 mm. 
Therefore along a 2'2 mm. ± to a 14'4 mm. Therefore H/V = IT, or e is < 56°, 
and, perhaps, about 53°. 
(4) January 13, 1915. a = 37° 21' S.W. A = 2280 km. Epicentre 42° 0' N., 
13° 42' E. 
Second phase sharp in E. 
South = 15 mm. West = 30 mm. Vertical = 66 mm. 
Therefore along a 30T mm. ± to a 14’8 mm. H/V about 0'5. Therefore 
e is < 56°, about 50°. 
These cases are in general agreement with the results of reflexion theory and 
encourage further examination. Great care has to be exercised in getting precisely 
corresponding pure movements in all three components, as within even a few seconds 
the resultant vibration changes rapidly and the peaks do not precisely correspond 
in all components. 
Case (l), fig. 5, illustrates this point very well. The first movement in S to East 
(which agrees precisely in time with the vertical motion up) reaches its maximum 
just as the North-south component begins to move. This second movement is first 
a little to South, then to North, the maximum throw to North coinciding in time 
with the maximum throw to West and the maximum throw down. Only a very 
open time scale shows this, and with a contracted scale we should probably have 
associated the first movements to East and to South together. 
In case (l) the second movement of S, which follows the first movement imme¬ 
diately, is South = 35 mm., West = 8'4 mm., Vertical = 3'0 mm. This gives 
