Velocity of Sound. 407 



at the times of the experiment, supposing it to be nearly the 

 same at both times. This agrees quite as nearly as could be 

 expected with the mean velocity of the wind determined by 

 the anemometer. 



Same day, May 23, half-past 1 1 A.M., barom. 29-67 inches: 

 *ahr. therm. 58°: air humid; wind as before. 



Before the gun was removed from Shooter's Hill, six rounds 

 more were fired. The intervals in which the sound reached 

 Kidbrook Lane, were 8"-l, 8"-125, 8"-13, 8"-15, 8'"1, and one 

 very doubtful. The mean of these is 8"-121. Distance 8820 

 feet. 



8820 



802T— 1086 feet > velocity of sound, opposed by the wind. 



Here the sound was but just audible, the wind diminishing 

 its intensity exceedingly. 



Same day, therefore, the gun was removed to Kidbrook 

 Lane, while I went back to Shooter's Hill. 



Half-past 12, barom. 29-67 inches; Fahr. therm. 60°; air 

 drier; wind as before. Six rounds were fired. The inter- 

 vals between the flash and the report were 7"-8, 7 7 *7 7"*8 

 7"*78, 7''*78, and one very doubtful ; mean 7"*77. 



8820 _ 



ipjY — 1 1 36 feet, velocity of sound, when aided by the wind. 



i ( 1086 + 1 1 36) = 1 1 1 3 feet, inferred velocity of the sound 

 independent of the wind; therm. 59°. \ (1136— 1086) = 25 

 feet inferred velocity of the wind, nearly as before. 



The same day, May 23, in the afternoon, the wind sub- 

 sided, so as not to exceed 6 or 8 feet per second, while the 

 temperature of the air remained nearly the same. I anxiously 

 availed myself of this opportunity to ascertain the velocity of 

 the sound, when scarcely affected by the wind. Mortars and 

 howitzers were firing from the battery, the former at an angle 

 of 45°, the latter at low angles for Ricochet practice. At 

 3£ P.M. when the barom. was at 29*68 inches, Fahr. therm, 

 at 60°, the sun shining, I took a station 3100 feet from the 

 battery, and in a direction nearly perpendicular to that of the 

 wind, then gently blowing. I observed the intervals between 

 the flash and the report, for six rounds, of which the first 

 three were with howitzers, the next three with mortars; these 

 were successively 2"-77, 2"-76, 2"-79, 2"-79, 2"-8, 2 "-8 ; their 

 mean 2''-786. 



2-786" = 1H2 feet, velocity of sound; therm. 60°. 



In these latter experiments the sound was very distinct and 



sharp : 



