406 Dr. Gregory on the 



Same day, quarter past 12, barom. therm, wind and weather 

 as before. 



Distance between the two bells 1650 feet; whole distance 

 3300 feet. Intervals elapsed in four experiments, 3' - 0, 3""0, 

 3"-0, 3"'0. 



^L— noo feet, velocity of sound; therm. 35°. 



Same day, half-past 12, barom. therm, wind and weather 

 as before. Distance between the two bells 1800 feet; whole 

 distance 3600 feet. Intervals elapsed in five trials, 3"*25, 

 3"-24, 3"-26, 3"-25, 3"-25 ; mean 3"*25. 



— — = 1108 feet, velocity of sound; therm. 35°. 



% (1098 + 1100 + 1108)= 1102 feet, mean velocity from this 

 day's experiments ; therm. 35°. 



Friday, May 23. This morning there was a tolerably brisk 

 wind blowing from the S.W. by W. nearly in the direction of 

 my Charlton and Kidbrook stations from Shooter's Hill. Of 

 this I gladly availed myself, as the morning was in other re- 

 spects favourable, in order to ascertain what would be the 

 effect of such a wind upon the velocity. Cloudy, air humid, 

 but no rain. 



I measured the velocity of the wind frequently with an ane- 

 mometer, and found it vary between 22 and 26 feet, the mean 

 24 feet. 



The gun a six-pounder, charge 8 oz. of powder. 1 1A.M. 

 gun at Shooter's Hill, sound heard at Charlton Lane, distance 

 6550 feet. Barom. 29-66 inches. Fahr. therm. 58°, air hu- 

 mid. Six rounds fired; the intervals were 6"'l, 6""05, 6''*0, 

 6"-05, 6"-0, 6''-04 ; their mean 6 7 '037. 



g-— = 1085 feet, velocity of sound, when opposed by the 



wind. 



Same day, quarter past 1 P.M., barom. 29 # 67 inches, 



Fahr. therm. 60° ; air drier. Gun at Charlton Lane. Sound 



heard at Shooter's Hill. Distance 6550 feet. Five rounds 



fired: the intervals were, 5'-65 doubtful, 5"'8, 5"'78, 5"*76, 



5 ""78, omitting the first, the mean interval of the other four is 



5"-78. 



6550 



„ = 1133^ feet, velocity of sound, when aided by the 



wind. 



\ (1085 + 11331) = 1109^ feet inferred velocity of sound in- 

 dependently of the wind ; therm. 59°. 



And £(1133^ — 1085)- 24£ inferred velocity of the wind 



at 



