64 The Eartliquahe of^lst Decemher, 1881. [Maech, 



from that time there was a succession of small waves at irregular intervals 

 until past midnight. 



At False Point, the diagram shows the passage of the earth-wave, or 

 forced sea-wave, at 7h. 54m. a. m. The pencil seems to have been moved 

 rapidly up and down a small distance for some minutes, and the clerk 

 notes that the building was shaken by an earthquake. The sea-wave here 

 is hardly indicated. Its first appearance is at llh. 12m. a. m., and there 

 is a second one at 1 p. m. 



At Dublat, the wave appears to have arrived at 1 p. m., and a second, 

 one hour afterwards ; there is also an indication of a third at 3 p. m. 



At Diamond Harbour, the indications of the wave are untrustworthy, 

 and very slight. If felt at all, it was at about 3 p. M. 



Looking over the data at our disposal, I find that the shock, i. e., the 

 earth- wave, was recorded as felt at Madras, Coconada, Vizagapatam, GopaU 

 pur, False Point, Calcutta, Port Blair, and Kisseraing, an island in the 

 Mergui Archipelago in latitude 11° 39' N., longitude 90° 31' E., and also on 

 board a ship, The Commonwealth^ in latitude 5* 55' N., longitude 92° 49' E. 



Of these the times of the shock at Madras, False Point, and Kisseraing 

 were probably recorded correctly within a minute. The time at Madras was 

 recorded in the Telegraph Office, and given to the nearest second. The 

 time at False Point was recorded on the tidal diagram, and also by Mr. 

 Eendell, of the Survey, who was leveling a few miles from False Point, and 

 whose recorded notice of the time at which he felt the shock agrees to the 

 minute with the tide-gauge record. 



At Kisseraing I was observing at the trigonometrical station there 

 with a 24" theodolite, and saw the earthquake before feeling it, the helio- 

 trope (distant some 15 miles) to which I was observing appearing to rise 

 and fall in the field of the telescope, and the levels of the instrument being 

 violently agitated. The motion was, to my feeling, barely perceptible, 

 but the recorder and other men with me said that they felt it distinctly. 

 It was not, however, felt by several of the officers of the Indian Marine, 

 who were on the island that morning, thus proving that it was not a severe 

 shock, though plainly noticeable by instrumental means. 



At Madras, False Point, and Kisseraing, the earth-wave was felt at 

 about the same minute — 7h. 55m. A. M. On the hypothesis that the strata 

 between them and the centre of impulse are homogeneous, this centre was 

 equi-distant from them, and would be at a spot in the Bay of Bengal in 

 latitude 11° 55' N. and longitude 89" 33' E. 



There is no reliable evidence on the subject of the velocity of earth- 

 waves ; it varies with the nature of the strata through which it passes and 

 the violence of the initial shock, and also on the depth of the locus of the 

 centre of impulse. 



