SOUFEIERE, AND ON A VISIT TO MONTAGNE PELFE, IN 1902. 
520 
and his colleagues.* It is the presence of a considerable, short, sharp depression, in 
advance of an elevation, which is more continued, and may last for a quarter of an 
hour or more. With these we rejjroduce also, by the kindness of the Meteorological 
Council, the trace left by the explosion of 12 tons of gunpowder on board the ship 
“ Lottie Sleigh,” lying in Liverpool Harbour, on the recording barograph at Liverpool 
Observatory, on January 15th, 1864. (Fig. 4.) The similarity between these waves 
is very striking : in each we have the initial, short, rapid fall, followed by an almost 
equally sudden rise, which lasts for a longer period, and is then succeeded in the 
Liverpool record by a second depression, not so great as the first. 
NOON 
MID. 
L POOL.JAN.15.1864. 
LOTTIE SLEIGH EXPLOSION 
^ Fig. 4.— Barographic tracing of the King’s barograph at the Liverpool Observatory, showing the effect 
of the ex]ilosion of twelve tons of gunpowder on board the “ Lottie Sleigh,” three miles distant. 
{Beproduced from the ^Proceedings of the Royal Society,' vol. xxxvi., PL I.) 
In the air waves which were produced by the eruption of Krakatoa these features 
Avere by no means so marked, and, in fact, Lieutenant-General Strachf.y was led to 
the conclusion, partly from his studies of the actual barographic tracings, and jDartly 
from the theoretical researches of Loi d Rayleigh, that “ the rise of the barometer 
indicating a sudden increase of pressure was the first and direct result of the 
explosion, and that the succeeding fall of the barometer . . . required some 
considerable time for its development.” 
The Sea Waves. 
We have ab'eady detailed the observations regarding sea Avaves occasioned by the 
great eruption of St. Vincent on May 7th in Barbados, Bequia, St. Lucia, Martinique, 
and Guadeloupe. {See p. 406 and p. 410.) In Barbados and in Bequia its amplitude 
Avas 2|- feet, in Martinique about 1 foot. Assuming that it originated in St. Vincent, 
and was synchronous with the great explosion and discharge of the avalanche of dust 
about 2 o’clock in the afternoon, Ave find that it took 70 minutes to cross the channel 
between that island and Barbados, where the first crest arrived at 3.10 p.m., and had 
a velocity of about 90 miles an hour. 
According to the preliminary inport of the French Commissioners, sea waves have 
been observed in Fort de France on the occasion of all the more important ei'uptions 
VOL. CC.-A. 
■* ‘ Comptes Kenclus,’ vol. cxxxv., p. 390. 
3 Y 
