54 Mr. Blanford on the Krakatoa Eruption. [March, 



History and Archaeology Committee. 

 Dr. Rajendralala Mitra. 

 Hon'ble J. Gibbs. 

 Major- General A. Cunningham. 

 Dr. J. Anderson. 

 R. R. Bayne, Esq. 

 J. Beanies, Esq. 

 Babu Pratapa Ch. Ghosha. 

 F. S. Growse, Esq. 

 Babu Pran Nath Pandit. 

 H. Rivett-Carnac, Esq. 

 Captain R. C. Temple. 

 Amir Ali, Esq. 

 E. F. T. Atkinson, Esq. 



Mr. Blanford exhibited the autographic trace of the Calcutta 

 barograph on the days 26th — 30th August 1883, and also reduced copies 

 of those of a number of European and American observations on the 

 same days, showing the effects of the eruption of Krakatoa. He remark- 

 ed — " At a meeting of the Royal Society on the 13th December, Mr. 

 R. Scott brought before the Society the originals of the European 

 barograms now exhibited, with reference to certain disturbances of the 

 barometer on the last days of August, and at the following meeting a 

 note was read by General R. Strachey, an abstract of which had been 

 published in Nature, in which it was shown that these disturbances were 

 referable to the eruption of Krakatoa, and afford evidence that an explo- 

 sion, which must have occurred at 9h. 32min. A. M. (Krakatoa local 

 time) at the volcano, had produced a concussion in the atmosphere that 

 had been propagated as an atmospheric wave not less than 3| times 

 round the earth and with a rate of progress nearly equal to that of the 

 sound wave, so that, while the branch of the wave moving from East to 

 West completed a revolution in 36 h. 57 min., that from West to East 

 accomplished the same distance in 35 h. 17 min. The disturbance 

 starting from Krakatoa spread out as a circular wave expanding to the 

 dimensions of a great circle, and then, contracting again to the antipodes 

 of Krakatoa, would expand again from that point as a circular wave 

 and return to its starting point and so on. As some of the European 

 bar o crams bore evidence of four transits of one limb of the wave 

 and three of the other limb, the wave must have accomplished 3| re- 

 volutions before it became evanescent. 



Computing the rate of progress from the intervals between the suc- 

 cessive transits of the waves, General Strachey has determined the 



