AS A VEHICLE OF SOUND. 
211 
“The firing took place at 1.40p.m. The guns proved were of comparatively small 
size — 64-pounders, with 10-lb. charges of powder. 
“ The concussion experienced at my house and office, about three quarters of a mile 
from the butt, was decidedly more severe than that experienced when the heaviest guns 
are proved with charges of 110 to 120 lbs. of powder. There was a de.nse fog here at 
the time of firing.” 
These were the guns heard by the inspector ; but on subsequent inquiry it was ascer- 
tained that two guns were fired at about 3 p.m. These were the guns heard by myself. 
Professor Abel also communicated to me the following fact : — “ Our workmen’s bell 
at the Arsenal Gates, which is of moderate size and any thing but clear in tone, is pretty 
distinctly heard by Professor Bloxam only when the wind is north-east. During the whole 
of last week the bell was heard with great distinctness, the wind being south-westerly. 
The distance of the bell from Bloxam’s house is about three quarters of a mile as the 
crow flies.” 
Slowly but surely we thus master this question ; and the further we advance the 
more we are assured that our reputed knowledge regarding it has been erroneous from 
beginning to end. Fogs have no such power to deaden sound as, since the time of 
Derham, has been universally ascribed to them. 
The vane on St. George’s Chapel, Albemarle Street, pointed west during these 
observations, but, judged by sensation, the air was dead calm. On the night of the 11th. 
the vane veered, and on the morning of the 12th it pointed N.E. The fog now attained 
its maximum density. I was unable to read at my window, which fronted the open 
western sky. At 10.30 I sent an assistant to the bridge, and listened for his whistle 
and pipe at the eastern end of the Serpentine. The whistle rose to a shrillness far 
surpassing any thing that I had previously heard, but it sank sometimes almost to 
inaudibility. At these special times of subsidence the organ-pipe came out distinctly. 
Acoustic clouds were drifting through the fog, and exercising a selective action on the 
sound. A second pipe, which was quite inaudible yesterday, was heard this morning. 
The fog was very dense. 
I exchanged places with my assistant and heard both the whistle and the pipe in my 
new position ; they were generally on the verge of inaudibility, and the pipe was only 
occasionally heard. Sometimes, however, both of them rose, to great distinctness. The 
rise and fall of the sound resembled the intermittent augmentation and diminution of 
light by the passage of clouds of varying density across the sun. We were able to dis- 
course across the Serpentine to-day with much greater ease than yesterday. 
On various occasions during our observations I had been able to fix the position of 
the Foreland in thick haze, and even in the acoustic shadow, by the direction of the 
sound. To-day I gave directions to Mr. Cottrell to come up to the Watermen’s 
Boathouse and sound his whistle as he came. He was entirely hidden by the fog ; and 
I walked along the opposite side of the Serpentine, clearly appreciating for a time that 
the line joining us was oblique to the axis of the river. At length I came to a point 
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