OBSERVATORIES AND THE DATA OBTAINED. 107 
The instrument used was a Milne horizontal pendulum, east component; photographic 
registration. 7 ,15 seconds; V,6.1; J, 340 meters; ¢€, 1.083; M7, 255 gm.; LD, 15.6 cm. 
Second preliminary tremors (?), 37.6"; interval, 25.1 minutes. Regular waves, 18.3"; 
interval, 65.8 minutes. Maximum amplitude, 2.0 mm. 
A glance at the seismogram will show the difficulty of getting satisfactory determina- 
tions of the times of arrival of the first two phases. The beginning at 13" 37.6™ certainly 
does not correspond with the beginning of the first preliminary tremors as this phase 
would be, for moderate and large distances, much weaker than was recorded at Perth; it 
is possible that this time refers to the second preliminary tremors. The times given 
accord with the marks on the seismogram; but in Circular 14 of the Seismological Com- 
mittee of the British Association for the Advancement of Science, the corresponding 
times are 2.4 minutes earlier. 
CAPE OF GOOD HOPE, AFRICA, 
Royal Observatory. Sir David Gill, director. 
Lat. 33° 56’ S.; long. 18° 29’ E.; altitude, 7 meters; distance, 148.63° or 16,524 km. ; 
chord, 12,266 km.; direction, 8. 86° E. 
Foundation, weathered Paleozoic rocks. 
Seismograms, sheet No. 1. 
The instrument used was a Milne horizontal pendulum, east component ; photographic 
registration. T7',, 12 seconds; V, 6.1; J, 220 meters; angular displacement, 1 mm. = 
0.21”; M, 255 gm.; L, 15.6:cm. 






PRELIMI- 
REG A - 
ee ere eae gee 
min. min. min. mm. 
East component. .| 36.5? 33.5? 34.0 0.2 
Interval «<<. .| 24.0? 81.0? 81.5 

The record is extremely small and is not brought out in the reproduction of the seis- 
mogram. On the photographic copy of the seismogram the line shows a slight swelling 
beginning at 13" 36.5", and a few long-period waves begin at 14" 33.5". It does not 
appear why this record is so much smaller than those of Perth and Mauritius. 
ISLAND OF MAURITIUS. 
Royal Alfred Observatory. T. F. Claxton, director. 
Lat. 20° 06’ S.; long. 57° 33’ E.; altitude, 51 meters; distance, 162.02° or 18,012 km.; 
chord, 12,601 km.; direction, N. 1° W. 
Seismograms, sheet No. 2. 
The instrument used was a modified Milne horizontal pendulum, two components; 
photographic registration. 
(1) North component: 7, 20.4 seconds; V, 11; J, 1,140 meters; ¢, 1.042; angular 
displacement, 1 mm. = 0.39”; M, 310+ gm.; L, 15 cm. (?) 
(2) East component: T, 20.4 seconds; V, 8; J, 830 meters; ¢, 1.007; angular dis- 
placement, 1 mm. = 0.25”; M, 340+ gm.; L, 13 cm. (?) 
Preliminary tremors, 41.2" (?); interval, 28.7" (?). Regular waves, 36.3" (?); in- 
terval 83.8 minutes (?). Maximum, 50.0". Amplitude, 5.0 mm. 
Duration, 3.3 hours. The times given do not specify the component, but apparently 
refer to the east component, as the north seismogram is not very clear. There is a con- 
