’upon Gun-powder , &c. 239 
city of the recoil from the chord of the arc through which the 
barrel afcended, is too well known to require an explanation : 
and it is alfo well known, that the velocities are to each other 
as the chords of thofe arcs. The lengths of thole chords, 
therefore, as they are fet down in the tables, are, in all cafes, 
as the velocities of the recoil. 
The powder made ufe of in thefe experiments was of the 
beft kind, fuch as is ufed in proving great guns at Woolwich. 
A cartridge, containing 12 lbs. of this powder, was given to 
me by the late General desaguliers of the Royal Artillery, 
and Infpe&or of Brafs and Iron Ordnance ; who alfo, in the 
politeft manner, offered me every other affiftance in his power 
towards completing the experiments I had projected, or in 
making any others 1 fhould propofe that might be ufeful in the 
profecution of my inquiries. 
This powder was immediately taken out of the cartridge, 
and put into glafs bottles, which were previoufly made very 
clean and dry ; and in thefe it was kept carefully fealed up till it 
was opened for ufe. When it was wanted for the experiments, 
it was weighed out in a very exaft balance, with fo much atten- 
tion, that there could not poffibly be an error in any inftance 
greater than one quarter part of a grain. The bottles were 
never opened but in fine weather, and in a room that was free 
from damp, and no more charges of powder than were necef- 
fary for the experiments of the day were weighed out at a time. 
Each charge was carefully put up in a cartridge of very fine 
paper, and thefe filled cartridges were kept in a turned wooden 
box, that was varnifhed on the infide as well as the outfide, to 
prevent its imbibing moifture from the air. 
The paper of which thefe cartridges were made was fo fine 
and thin, that 1280 fheets of it made no more than an inch in 
2 K 2 thicknefs, 
