128 Dr. GreGory on the 
this opportunity to ascertain the velocity of the sound, when 
scarcely affected by the wind. Mortars and howitzers were firmg 
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. 
ae =1112 feet, velocity of sound ; therm. 60°. 
In these latter experiments the sound was very distinct and 
sharp: the result, though drawn from a short distance serves to 
confirm the preceding results on the same day. 
Thursday, August 7. On this day, which was cloudy, but with 
intervals of sunshine, I employed the same 6 pounder as before: 
sometimes with charges of 8 oz. of powder, at others, when the 
distance required it, with 12 oz. The wind was quite brisk, varying 
in velocity from 30 to 35 feet, as determined by an anemometer. 
At eleven o’clock a.m. barom. 29.80 inches; Fahr. therm. 66° ; 
air dry, cloudy, but sun shining; wind nearly opposing the motion 
of the sound, and having a velocity of 30 feet. Sta rounds were 
fired from Shooter's Hill. The intervals occupied in the passage of 
sound from thence to Kidbrook Lane, distance 8820 feet, were 8”.1, 
87.15, 8".16, $”.13, 8”.13, 5”.12; their mean, 8.13. 
8820 
S13 7 1085 feet, velocity of sound, when opposed by the wind. 
Same day, August 7, quarter past 1, p.m. barom. therm. wind 
and weather as before. 
The gun being placed in Kidbrook Lane, I went to the station 
