Sufferings of Birds 
a 
of the almost incessant noise associated with 
these establishments, the birdsin general did 
not seem to avoid them. It was, however, 
recorded that two large ancient ROOKERIES, 
one about a quarter and the other half a mile 
away, were deserted in I9I15 on account of a 
field being used habitually for the descent of 
aeroplanes (Observer, 5.1X.15). 
Sound-waves of great explosions have been 
found to travel long distances from the centre 
of the disturbance. When the Silvertown 
munitions factory exploded in East London 
on January roth, 1917, it was heard 128 miles 
away (Proc. Roy. Soc. Edtn., vol. xxxviii. 
p. 115), and other great explosions have been 
distinguished at distances varying from 90 
to 186 miles (Nature, 1917, p. 439). A limited 
number of observations tend to show that 
throughout a large part of the area over 
which the sound-waves are audible, birds are 
affected by the disturbance. The immediate 
cause of their disquiet is unknown, but it is 
supposed to be due either to actual percep- 
tion of the sound of explosions or to shock 
caused by air-wave concussion (Scottish 
84 
