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distance of 6 miles. The superiority of the 18-pounder gun, 
already employed by the Trinity House as a fog-signal, over 
horns and whistles, was on this day so decided as almost to 
warrant its recommendation to the exclusion of all the other 
signals. 
Ho thing occurred on June 2 to exalt our hopes of the 
trumpets and whistles. The horns were scarcely heard at a 
distance of 3 miles ; sometimes, indeed, they failed to be heard 
at 2 miles. By keeping everything quiet on board, they were 
afterwards heard to a distance of 6 miles — a result, however, 
mainly due to the improved condition of the atmosphere. 
Considering the demands as to sound-range made by writers on 
this subject, the demonstrated incompetence of horns and 
whistles of great reputed power to meet these demands was not 
encouraging. On June 3 the atmosphere had changed sur- 
prisingly. It was loaded overhead with dark and threatening 
clouds ; the sounds, nevertheless, were well heard beyond 
9 miles. On June 10 the acoustic transparency of the air was 
also very fair, the distance penetrated being upwards of 8f 
miles. The subsidence of the sound near the boundary of the 
acoustic shadow on the Dover side of the Foreland, and before 
entering the shadow, was to-day sudden and extraordinary, 
affecting equally both horns and guns. We were warned on 
June 3 that the supremacy of the gun on one occasion by no 
means implied its supremacy on all occasions, the self-same 
guns which on May 20 had so far transcended the horns being 
on this day their equals and nothing more. June 11 was 
employed in mastering still further the facts relating to the 
subsidence of the sound east and west of the Foreland; the 
cause of this subsidence being in part due to the weakening of 
the sonorous waves by their divergence into the sound shadow, 
and in part to interference. 
The atmosphere on June 25 was again very defective acous- 
tically. The sounds reached a maximum distance of 6-^ miles ; 
but at 4 miles, on returning from the maximum distance, they 
were very faint. The day had, as it were, darkened acousti- 
cally. On this day the guns lost still further their pre- 
eminence, and at miles were inferior to the horn. Ho 
sounds whatever reached Dover Pier on the 11th; and it was 
only towards the close of the day that they succeeded in 
reaching it on the 25th. Thus by slow degrees the caprices 
of the atmosphere made themselves known to us, showing us 
subsequently that within the limits of a single day, even within 
a single minute, the air, as a vehicle of sound, underwent most 
serious variations. June 26 was a far better day than its pre- 
decessor, the acoustic range being over 9^ miles. The direction 
of the wind was less favourable to the sound on this day than 
