AS A VEHICLE OF SOUND. 
221 
waves was manifested. At 3 p.m. the case was completely altered, for then the high- 
pitched syren was heard when all the other sounds were inaudible. On many other 
days we had illustrations of the varying comparative power of the syren and the guns. 
On the 9th of October sometimes the one, sometimes the other was predominant. On 
the morning of the 13 th the syren was clearly heard on Shakespeare’s Cliff, where two 
guns with their puffs perfectly visible were unheard. On October 16, 2 miles from the 
signal-station, the gun at 11 o’clock was inferior to the syren, but both were heard. At 
12.30, the distance being 6 miles, the gun was quite unheard, while the syren continued 
faintly audible. Later on in the day the experiment was twice repeated. The puff of 
the gun was in each case seen, but nothing was heard ; in the last experiment, when the 
gun was quenched, the syren sent forth a sound so strong as to maintain itself through 
the paddle-noises. The day was clearly hostile to the passage of the longer sonorous 
waves. I may anticipate matters so far as to say that on this day the syren heard at 
Shakespeare’s Cliff surpassed the gun, while at the South Sand Head light-vessel the gun 
surpassed the syren. In the former case a light wind opposed, and in the latter case 
favoured the sound ; and the opposition of the wind proves in all cases more damaging 
to the gun than to the syren. 
October 17 began with a preference for the shorter waves. At 11.30 a.m. the mastery 
of the syren over the gun was pronounced ; at 12.30 the gun slightly surpassed the 
syren; at 1, 2, and 2.30 p.m. the gun also asserted its mastery. This preference for the 
longer waves was continued on October 18. On October 20 the day began in favour 
of the gun, then both became equal, and finally the syren gained the mastery : but the 
day had become stormy, which is always a disadvantage to the momentary gun-sound. 
The same remark applies to the experiments of October 21. At 11 a.m., distance 
6-| miles, when the syren made itself heard through the noises of wind, sea, and paddles, 
the gun was fired ; but, though listened for with all attention, no sound was heard. 
Half an hour later the result was the same. On October 24 five observers saw the flash 
of the gun at a distance of 5 miles, but heard nothing ; all of them at this distance heard 
the syren distinctly : a second experiment on the same day yielded the same result. On 
the 27th also the syren was triumphant ; and on three several occasions on the 29th its 
mastery over the gun was still more pronounced. Such experiments yield new con- 
ceptions as to the scattering of sound in the atmosphere. No sound here employed is 
a simple sound ; in every case the fundamental note is accompanied by others, and the 
action of the atmosphere on these different groups of waves probably has its optical 
analogue in that scattering of the light-waves which produces the various shades and 
colours of the sky. 
I have just glanced at the observations made on October 17 ; but, as this proved our 
day of maximum acoustic transparency, I will here introduce a fuller record of the 
day’s proceedings. Mr. Holmes having expressed a wish to sound his four horns 
together, the day was devoted to comparing them with the syren. The barometer had 
been rising during the whole of the previous day, the wind being W.S.W. This 
