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PROFESSOR TYNDALL ON THE ATMOSPHERE. 
§ 16. Action of Wind. 
The action of wind upon sound has been frequently observed, and a statement of 
Dr. Robinson’s regarding it has been already quoted (§ 2). In stormy weather we were 
frequently forsaken by our steamer, which had to seek shelter in the Downs or Margate 
Roads, and on such occasions the opportunity was turned to account to determine the 
effect of the wind. On October 11, accompanied by Mr. Douglass and Mr. Edwards, 
I walked along the cliff from Dover Castle towards the Foreland, the wind blowing 
strongly against the sound. On the Dover side of the Cornhill Coastguard Station 
(see Map, Plate XIX.), and at about a mile and a half from the Signal-Station, on the 
edge of a deep hollow or combe, we first heard the faint but distinct sound of the syren. 
The horn-sound was inaudible. A gun fired during our halt was also unheard. 
Descending the combe the syren-sound vanished as we plunged more deeply into the 
acoustic shadow. On the eminence close to the Coastguard Station the wind was very 
violent and noisy ; sheltering ourselves as well as we could behind some mounds, we 
listened for the sounds, but heard nothing. No sounds had been heard during the day 
by the coastguard men. 
At the edge of the next combe we caught the sound of the syren, which continued to be 
heard as we walked round the combe. As we approached the station we saw the smoke 
of the gun. Mr. Edwards heard a faint crack, but neither Mr. Douglass nor myself 
heard any thing. The sound of the syren was at the same time of piercing intensity. 
We waited at this spot for ten minutes, when another gun was fired. I thought I 
heard a faint thud, hut could not he certain. My companions heard nothing. On 
pacing the distance afterwards it was found to be only 550 yards. We were shaded at 
the time by an eminence from both the syren and the gun, and more deeply shaded 
from the latter than from the former; but the difference could not account for the 
utter extinction of the gun-sound at a time when the syren sent to us a note of great 
power. Subsequent experiments, moreover, confirmed the conclusion to which this one 
points, that an opposing wind affects the gun-sound far more seriously than that of the 
syren. 
Requesting Mr. Ayres to walk to windward along the cliff and to note and report 
upon the sounds, and asking Mr. Douglass to proceed to St. Margaret’s Bay, during their 
absence I had 3 guns fired. Mr. Ayres heard only one of them. Favoured by the 
wind, Mr. Douglass, at twice the distance, and far more deeply immersed in the sound- 
shadow, heard all three reports with the utmost distinctness. 
Joining Mr. Douglass, we continued our walk to a distance of f of a mile beyond 
St. Margaret’s Bay. Here, being dead to leeward, though the wind was as violent as it 
had been at the coastguard station, the sound of the syren was borne to us with extra- 
ordinary power*. In this position we also heard the gun loudly, and two other loud 
reports at the proper interval of ten minutes, as we returned to the Foreland. 
To windward of the instruments, Mr. Edwards noticed a rapid and considerable falling 
* The horn here was temporarily suspended, hut doubtless would have been well heard. 
