\ 
^oo Mr. Thompson’s Experiments 
far or farther than the proof mark, the powder is as good or 
better than the fhmdard ; but if it falls fhort of that diftance, 
it is worfe than the ftandard, and is to be rejected. 
For the greater the velocity is with which the bullet is im- 
pelled, the greater will be the recoil; and when the recoil is 
the fame, the velocities of the bullets are equal, and the pow- 
der is of the fame degree of ftrength, if the quantity of the 
charge is the fame. And if care is taken in proportioning the 
charge to the weight of the bullet, to come as near as poftible 
to the medium proportion that obtains in practice, the deter- 
mination of the goodnefs of gun-powder from the refult of 
this experiment cannot fail to hold good in a&ual fervice. 
Fig. 14. reprefents the propofed apparatus, drawn to a fcale 
of one foot to the inch, a , b, is the barrel fufpended by the 
pendulous rods r, d ; and r is the ribbon for meafuring the 
recoil. 
The length of the bore is 30 inches, and its diameter is one 
inch, confequently it is juft 30 calibres in length, and will 
carry a leaden bullet of about 3 ounces. 
The barrel may be made of gun metal, or of caff iron as 
that is a cheaper commodity ; but great care mu ft be taken in 
boring it, to make the cylinder perfedtly ftrait and fmooth, as 
well as to preferve the proper dimenftons. Of whatever metal 
the barrel is made, it ought to weigh at leaft 50 lbs. in order 
that the velocity of the recoil may not be too great ; and the 
rods by which it is fufpended fhould be five feet in length. The 
vent may be about one twentieth of an inch in diameter ; and it 
fhould be bouched or lined with gold, in the fame manner as the 
touch-hole is made in the better kind of fowling pieces, in 
order that its dimenftons may not be increafed by repeated 
firing, 
2 The 
