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POPULAR SCIENCE REVIEW. 
found inferior to it. This was our day of greatest acoustic 
transparency, the sound reaching a maximum of fifteen miles 
for the syren, and of more than sixteen for the gun. The 
echoes on this day were continued longer than on any other 
occasion. They continued for fifteen seconds, their duration 
indicating the atmospheric depth from which they came. 
On October 18, though the experiments were not directed 
to determine the transmissive power of the air, we were not 
without proof that it continued to be high. From 10 to 
10.30 a.m., while waiting for the blasts of the syren at a 
distance of three miles from the Foreland, the continued re- 
ports of what we supposed to be the musketry of skirmishing 
parties on land were distinctly heard by us all. We afterwards 
learned that the sounds arose from the rifle practice on Kings- 
down beach, 5J miles away. On July 3, which, optically con- 
sidered, was a far more perfect day, the 1 8-pounder, howitzer, and 
mortar failed to make themselves heard at half this distance. The 
18th was mainly occupied in determining the influence of pitch 
and pressure on the syren-sound. Taking the fluctuations of 
the atmosphere into account, I am of opinion that the syren, 
performing from 2,000 to 2,400 revolutions a second, or, in 
other words, generating from 400 to 480 waves per second, best 
meets the atmospheric conditions. We varied the pressure 
from 40 to 80 lbs. on the square inch ; and though the in- 
tensity did not appear to rise in proportion to the pressure, 
the higher pressure yielded the hardest and most penetrating 
sound. 
The 20th was a rainy day with strong wind. Up to a 
distance of 5J miles the syren continued to be heard through 
the sea and paddle-noises. In rough weather, indeed, when 
local noises interfere, the syren-sound far transcends all other 
sounds. On various occasions to-day it proved its mastery over 
both gun and horns. On the 21st the wind was strong and the 
sea high. The horn-sounds, with paddles going, were lost at 
four miles, whilst the syren continued serviceable up to 6|- 
miles. The gun to-day was completely overmastered. Its 
puffs were seen at the Foreland ; but its sound was unheard 
when the syren was distinctly heard. Heavy rain failed to 
damp the power of the syren. The whistles were also tried to- 
day, but were found far inferior to the syren. On the 22nd it 
blew a gale, and the Galatea quitted us. We made obser- 
vations on land on the influence of the wind and of local noises. 
The shelter of the Coastguard Station at Cornhill enabled us to 
hear gun-sounds which were quite inaudible to an observer out of 
shelter ; in the shelter also both horn and syren rose distinctly in 
power; but they were also heard outside when the gun was 
quite unheard. As usual, the sound to leeward was far more 
