1883.] Lt.-Gen. R. Strachey. Barometrical Disturbances. 143 



exhibits considerable similarity to that of the King's barograph at 

 the Liverpool Observatory, at the Waterloo Docks Pierhead on the 

 15th of January, 1864, when the "Lottie Sleigh," loaded with about 

 twelve tons of gunpowder, blew up. The ship was lying about three 

 miles from the Observatory. I am indebted to the kindness of Mr. 

 Hartnup for a tracing of this interesting curve. 



In this preliminary note I can only say that until copies of the 

 barograms from extra- European stations, such as New Zealand, the 

 Havana, and Calcutta, are received, it is impossible to see whether 

 the phenomena so marked in their occurrence in Europe have 

 manifested themselves elsewhere ; at Toronto they appear to have 

 been recorded. On that subject I shall hope to lay a future communi- 

 cation before the Society. 



II. Note on the foregoing Paper. By Lieutenant -General R. 

 Strachey, F.R.S. Received December 12, 1883. 



The obvious correspondence of the forms and times of occurrence of 

 the barometric disturbances, described in Mr. Scott's paper, at once sug- 

 gested that they were due to a common origin, and the great volcanic 

 eruption at Krakatoa in the Straits of Sunda appeared to supply a 

 probable efficient cause. Any shock of sufficient violence might 

 be expected to produce an atmospheric wave, advancing from the 

 place where it was caused in a circular form round the globe, at first 

 expanding until it had got half round the earth, and then again con- 

 tracting till it was again concentrated at the antipodes, from which 

 again it would be thrown" back, and so pass backwards and forwards 

 till it was obliterated. It might also have been expected that such a 

 wave would travel with the velocity of sound, being probably of the 

 same nature as that which causes sound, though the vibrations had 

 not the peculiar character that affects our organs of hearing. It has, 

 however, been suggested to me that the wave may rather have had 

 the character of a solitary wave produced in a liquid, the velocity of 

 which in the air would not materially differ from that of sound. 



A rough examination of the facts at first made known by the obser- 

 vations recorded in Great Britain indicated that there w r as prima faeie 

 strong evidence in support of this view, and that the phenomena 

 would be approximately explained by the passage round the earth of 

 a series of waves travelling at the rate of about 700 miles an hour 

 in opposite directions from the place where the volcanic eruption 

 occurred. The records since procured from other places, and the more 

 careful examination of the facts, has quite confirmed this conclusion. 



Although we may expect to obtain additional data from other parts 



