1917-18.] Sound-Waves of the East London Explosion. 
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XII. — The Sound-Waves and other Air- Waves of the East London 
Explosion of January 19, 1917. By Charles Davison, Sc.D., 
F.G.S. Communicated by The General Secretary. 
(MS. received April 29, 1918. Read June 3, 1918.) 
The explosion which occurred in East London at 6.51 p.m. on January 19, 
1917, was one of the greatest ever experienced in this country. The site of 
the explosion is indicated approximately by the star in the accompanying 
maps. The total amount of explosives lost is known, if at all, only to those 
in authority. 
In order to determine the forms of the sound-areas, I wrote letters to 
most of the principal newspapers published in London and within and near 
the districts concerned, and I am greatly indebted to the courtesy of many 
editors in allowing me space for which there were so many important 
claims, and also to the numerous correspondents who so kindly answered 
my inquiries. After the boundaries of the sound-areas had been drawn 
from an unusually large number of positive records, I wrote to the 
incumbents of many parishes in small towns and large villages, and to 
superintendents of police within the silent zone and just within and for 
some distance outside the boundaries of the sound-areas as I had drawn 
them. The total number of positive records is 571 from 391 places, and of 
negative records 75 from 71 places. In addition to these, there are 79 
records from 71 places at which the sound was apparently not observed, 
but at which windows were shaken or pheasants disturbed ; making a total 
of 725 records from 533 places. 
Form and Dimensions of the Sound- Are a. 
The form of the sound-area is shown in tig. 1. It consists of two 
detached portions, the inner and outer sound-areas, between which lies 
the silent zone. The places at which the sound was heard (omitting many 
of those within the London area) are indicated by dots ; those at which it 
, was not heard, so far as is known, by small circles. Places from which 
doubtful records have been received are denoted by small crosses. Within 
the whole silent zone, as drawn in fig. 1, there is only one place (Ipswich) at 
which the sound was heard, and even there, I believe, by but one observer; 
and two others (Uppingham and Lilford) at which it may have been heard. 
