408 Dr. Gregory on the 



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 six-pounder 

 as before, sometimes with charges of 8 ounces of powder, at 

 others, when the distance required it, with 12 ounces. 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. Six 

 rounds were fired from Shooter's Hill. The intervals occu- 

 pied in the passage of sound from thence to Kidbrook Lane, 

 distance 8820 feet, were 8"'l, 8"-15, 8"'16, 8"'13, 8'"13, 8'"12; 

 their mean, 8"'13. 



®^- = 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 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. 



= 1145i feet, velocitv of sound, when aided by a wind 



77 " " • 



of about the same velocity as the former. 



£ ( 1 085 + 1 1 45 j) = 1 1 1 5^ feet, velocity of sound s therm. 66°, 



1(1145^ — 1085) = 30^ feet, velocity of the wind. 



Same day, August 7, halt-past 11 A.M., barom. 29-80 

 inches ; Fahr. therm. 64°, the wind blowing in the same di- 

 rection as before, with (an estimated) velocity of 30 feet; air 

 dry, cloudy, no sun. The same six-pounder gun was fired 

 from the Shooter's Hill station with a charge of 12 ounces of 

 powder, and I took a station on Blackheath 20 feet further 

 than on January 9, its distance being 13,460 feet from the 

 gun. 



Six rounds were fired ; one of the intervals was very doubt- 

 ful ; the others were 12'"4, 12"-38, 12''-42, 12"'38, 12'-4, 12"-4; 

 their mean 12''-396. 



= 1085*8 feet, velocity of sound when opposed by the 



wind. 



Being fearful of bringing the gun to Blackheath, in the vi- 

 cinity 



