Velocity of Sound. 129 
on Shooter’s Hill. Six rounds were fired, and the intervals occupied 
in the transmission of the sound were 7.7, 7".75, 7'.68, 7".67, 7”.72, 
7.68 ; their mean 7”.7. 
8820 
7-7 
about the same velocity as the former. 
4(1085+ 11454) = 11154 feet, velocity of sound; therm. 66°, 
4(11454 — 1085) =304 feet, velocity of the wind. 
Same day, August 7, half past 11, a.m. barom. 29.80 inches; 
Fahr. therm. 64°, the wind blowing in the same direction as before, 
with (an estimated) velocity of 30 feet; air dry, cloudy, no sun. 
The same 6 pounder gun was fired from the Shooter’s Hill station 
with a charge of 12 oz. of powder, and I took a station on Black- 
heath 20 feet farther than on January 9, its distance being 13460 
feet from the gun. 
Six rounds were fired, one of the intervals was very doubtful ; 
the others were 12”.4, 12’.38, 12”.42, 12.38, 12".4, 12”.4; their mean 
12” .396. 
12.396 
Being fearful of bringing the gun to Blackheath, in the vicinity 
of so many carriages as were incessantly passing, I could not here 
avail myself of the benefit of comparing the above intervals with 
those in which the direction of the transmission should be reversed. 
I venture, therefore, to add the velocity of the wind to that of 
the sound, as obtained by the experiment, and thus obtain 
1085.8+30=1116 feet nearly, for the velocity of sound, the therm. 
standing at 64°. 
Monday, August 18. On this day, the same 6 pounder gun was 
placed upon the wharf by the side of the Thames in the Royal 
Arsenal, and I took a station at the opposite extremity of the 
Gallion’s Reach, not far from the mouth of Barking Creek ; the 
Vol. (1. Part 1. R 
=11454 feet, velocity of sound, when aided by a wind of 
= 1085.8 feet, velocity of sound when opposed by the wind. 
