1897-98.] Note on Indian Earthquake , 12 th June 1897 . 
11 
A Short Note on the Disturbance of the Magnetical 
and Meteorological Instruments at the Colaba Ob- 
servatory during the Earthquake of 12th June 1897. 
By N. A. Moos, Director of the Observatory. 
(Read December 6, 1897.) 
The four instruments, the traces of which are examined, are the 
declination, horizontal force, and vertical force magnetographs, and 
the barograph. The instruments being not seismological, the fol- 
lowing discussion of the character of the disturbance, based upon 
the traces of these instruments, must obviously be regarded as an 
attempt at explanation, and as an attempt only. Colaba, it 
appears, was situated well outside the area of perceptible shaking, 
and the distance of the Observatory from the centre of disturbance, 
whether suboceanic or otherwise, was sufficiently large to render 
the disturbance as it reached Colaba very feeble, and yet it was 
just sufficiently strong to leave some record of its peculiar charac- 
teristics. All traces have been enlarged about two and a half 
times, but the exact time and measurements have been derived 
from the original traces. 
It must be noted here that the disturbance fortunately occurred 
just after 16 hours, the time of hourly eye observations. A valu- 
able opportunity therefore was secured, and it became possible to 
note and study the peculiar behaviour of the instruments during 
their disturbances, some of which, by the rapidity of their move- 
ments, could not have been photographed. There may be some 
doubt as to whether the disturbance in the magnetographs was due 
to mechanical or magnetic action, but no such doubt can exist for 
the barograph. The disturbance of this instrument must have 
been caused by distortional waves, or due to tilting of the instru- 
ment. It will be noticed that the maximum effect of the disturb- 
ance, as photographed in the barograph trace, followed the largest 
