AS A VEHICLE OF SOUND. 
239 
Afloat. Ashore. 
Wind N.N.W. and W.N.W., 2 to 3 N.W., 2 
Barometer .... 30-00 29-6 
Wet bulb 54° to 57° 55° to 48° 
Dry „ 57° to 61° 59° to 52° 
October 15. Partial Summary . — Inspected Dungeness rotating fog-horn. Maximum range, -with horn 
pointed on us, 3-9 miles, then barely audible : lost at 4 miles. Report of gun much louder than direct sound 
of horn at 3-9 miles. In the other medial line range of horn still less. Aerial echoes of 4 seconds duration 
returned in every case from the direction in which the horn was pointed. 
Afloat. Ashore. 
Wind nil — 
Barometer 30-00, falling — 
Wet bulb ; 55° — 
Dry „ 59° — 
October 16. Partial Summary . — Maximum range in axis 5 miles : syren faintly heard ; gun seen but 
not heard. With paddles going syren heard at 3| miles in axis ; gun seen but not heard at 2~ miles. Round 
arc of 2 miles radius from South Foreland the results were as follows : — Deep in sound-shadow on Dover side 
syren much enfeebled ; Canadian whistle at times equal to it ; gun yielded only a thud. In sound-shadow 
on South Sand Head side the syren was again much enfeebled, and at times surpassed by the Canadian 
whistle: here the gun gave a loud report, there being a component of wind in favour of the sound. On 
clearing the shadows of the intervening projecting cliffs on either side all the sounds were much louder; and 
on nearing the axis of the syren its sound rose to an extraordinary intensity, surpassing the loud report of 
the gun. 
The Canadian whistle has shown itself much superior to the other whistles. 
Afloat. 
Ashore. 
Wind 
W.S.W., 2 to 3 
S.W., 3 
Barometer 
30-2 
29-9 
Wet bulb 
60° to 56° 
55° to 48 c 
Dry 
64° to 60° 
60° to 51 c 
October 17. Partied Summary . — Four horns tried against syren : proved inferior to it. A day of great 
acoustic transparency. Maximum range with vessel stopped, gun 16| miles, dull report ; syren and horns 
heard occasionally at 1T> miles in axis. Early in the day, with paddles going, syren heard at 7 miles in axis, 
while gun and horns were inaudible at 5| miles. In sound-shadow, Dover side, syren proved itself superior to 
gun and horns. The limit of the sound-shadow was to-day very sharply defind. At the base of the South 
Foreland cliff the aerial echoes of the syren-sound lasted from 14 to 15 seconds : the echoes were observed to 
strike in upon the direct sound one second after commencement of the actual blast. 
Afloat. Ashore. 
Wind calm and N.E., 1 S.E., 1 
Barometer 30-2 29-9 
Wet bulb 54° to 61° 54° to 50° 
Dry „ 57° to 66° 60° to 54° 
October 18. Partial Summary . — Experiments on pitch and pressure of syren. At 2 miles 2400 probably 
better than 1500 revolutions per minute. The greater pressure yields the harder and firmer sound. Reports 
heard in the morning proved to come from rifle practice on Kingsdown beach, 5^ miles off, or twice the distance 
at which cannons were heard on July 3. Dead to leeward, about 4 miles, missed hearing a gun through not 
attending. Gun requires a prepared attention to hear it. 
