4.04- Dr. Gregory on the 



tween observing the flash and hearing the report, were 3"'25, 

 3"-28, 3"'S, 3"-3, 3"'32 ; mean 3"-29. 



^- = 1 094-2 feet, velocity of sound; therm. 27°. 



The sound of the same charge, fired from the same mus- 

 quet, was heard much more intensely on this clear frosty 

 night than in the day-time of January 3, at the same distance, 

 3600 feet. 



Same day, January 9. Being anxious to extend die experi- 

 ments to greater distances, I had previously applied to Ge- 

 neral Ramsey, of the Royal Artillery, the Commandant of the 

 Garrison here, for the use of cannons as well as musquets : 

 these, with his accustomed courtesy and kindness, he imme- 

 diately ordered to be at my disposal whenever I should need 

 them in the course of my experiments. 



On the morning of this day, therefore, I chose a station for 

 the gun on the side of Shooter's Hill, between Severn-Droog 

 Castle and the 8 mile-stone on the Dover road. I selected 

 three other stations from which the gun could be seen with 

 a good Theodolite telescope ; one of these was at the entrance 

 of the lane turning from the Dover road to Charlton, between 

 " the Sun in the Sands" and the 7 mile-stone; the second in 

 the Kidbrook Lane which turns off from the Dover road be- 

 tween the 6 mile-stone and " the Sun in the Sands;" and the 

 third on Blackheath, nearly in a continuation of the western 

 wall of Greenwich Park towards the windmills. These three 

 stations are probably 200 feet above the high water-mark in 

 the Thames at Woolwich ; and the station at which the gun 

 was placed is still more elevated. 



The distances, as accurately measured, were, from the 

 Shooter's Hill station to that in Charlton Lane 6550 feet; 

 from Shooter's Hill to that in Kidbrook Lane 8820 feet; from 

 the Shooter's Hill station to that on Blackheath, 13,440 feet. 



The gun employed was a six-pounder, the charge of pow- 

 der eight ounces. The serjeant-major who remained at the 

 gun was directed to order the men to commence firing at a 

 certain minute by his watch (which was previously made to 

 agree with mine), and then to fire regularly a certain number 

 of rounds at intervals of two minutes: this was the practice 

 throughout the experiments, the gun was always pointed to- 

 wards me, at a very small elevation, except it be otherwise 

 expressed. 



January 9th, noon. Barom. 29'92 inches ; Fahr. therm. 

 33°; weather dry, wind scarcely perceptible, a clear cloudless 

 frosty day. 



Six 



