FORE-SHOCKS AND AFTER-SHOCKS. 
55 
The sympathetic subsidiaiy shock, which I first Supposed to 
have had its origin under the Bay of Bengal, now appears to have 
originated in the neighbourhood of Madura and to have occurred at 
about 10 hours 26 minutes. Its existence is further indicated by 
the disturbance to the Madras sidereal clock about a minute before 
the long waves from the Srimangal centrum could have reached 
Madras, and the subsidiary earthquake record superimposed on the 
Rocca di Papa seismograms corresponding with the time when the 
long waves from this Madura centrum would be expected to reach 
Rome tends to confirm this. It is not recognizable on the British 
seismograms, presumably because Britain is too far for such a weak 
shock to be recorded, and it is not recognizable on the Indian 
seismograms, other than those of Colombo and Kodaikanal since the 
calculated time of arrival at the various observatories corresponds 
to a time when the recording instruments were recording violent 
long waves from the Srimangal earthquake, although certain maxima 
on the records are somewhat significant. Rocca di Papa however, 
seems to have been sufficiently far away for the record of the Sri- 
mangal Long waves not to be too violent to obscure superimposed 
waves, and at the same time not to have been too far away for the 
detection and registration of the long waves from the Madura centrum, 
and its seismograms practically prove the existence of the subsidiary 
shock. 
