ox SEISMOLOGICAL IX\'KSTIGATION. 



243 



Magnetometer Disturbances eeoobdhd at the Royal Alfred 

 Observatory, MAVRiTius—continued. 



No. 



No. on 

 List 

 p. 227 



Month 



Day 



Time of 

 Earthquake 



Magnetic Disturbances 



1897 



40 



41 

 42 

 43 



44 



9 18 P.M. 



11 29 A.M. 

 7 24 P.M. 

 5 28 A.M. 



11 40 A.M. 



H 4h. 40m. P.M. va, small distance after 



until midnight. V like H 

 H 2h. 10m. P.M. a 

 D 4h. 10m. A.M.-5h. 10m. vs 

 H uh. 40m. A.M.-lOh, 10m. vs 

 H small disturbance all day, sharp at 



4h. 15m. P.M.-4h. 35m "V like H, 



only very small 



An examination of the above table, for which I am indebted to Mr. 

 T. F. Claxton, the Director of the Royal Alfred Observatory, shows the 

 following results : — 



Cases in whicJi magnetic needles have been disturbed at intervals 

 varying between a few minutes and 30 hours before an earthquake, 32. 



Cases in which magnetic needles have been disturbed at intervals 

 varying between a few minutes and 6 hours after an earthquake, 11. 



Case in which the disturbances of magnetic needles have accompanied 

 an earthquake, 1. 



Observations at the Magnetic and Meteorological Observatorg, Batavia. 

 By Dr. J. P. van der Stok. 



June 12, 1897 (Assam Earthquake) (.see Earthquake No. 105). 



G.M.T. 



Tlic declinometer and balance were not disturbed. 



September 21, 1897 (see Earthquake No. 134) 

 Horizontal Force . , 



Declination at , 

 Vertical Force 

 Electrometer 



H. 



5 

 5 

 5 

 .5 

 5 

 5 



M. 



19 

 25 

 39 

 26 

 23 

 21 



S. H. 



20 A.M. 5 

 20 5 



20 and 5 



M. 



24 

 30 

 42 



s. 

 20 

 20 

 20 



20 



20 A.M. slight. 



20 (maximum). Duration 20 mins. 



20 A.M. (commencement). 



The distance from Batavia to the origin of these last two disturbances 

 is 1,500 kni.s. The last of them also disturbed magnetometers in tlie 

 Mauritius, Bombay, Pola, and Utrecht. 



