TRACT 34.

IN GUNNERY.

335

p = 66011)

g 78 inches or 6^ feet,

'o — 84 inches or 7 feet,i = 90 inches or 7-| feet,

Here the value of v is 1500,Hence = x ——— :

the ball being cast iron,its diameter 1'96 inches,and its weight 1-^ or -filb.also the value of z is 14 inch,or feet.

and z = 14 inches or feet.

660.13.7.6.67 1500.1500

4 hz pgo + bii 2.4.16.7.64 660.61.7 +

152 '

15

= 32000 nearly, which is the value of Ii for a ball of thatsize and weight. Or the resistance in this instance is 32000times the force of gravity.

= -4-, part of a foot, or

Hence also x = ——- x ———4 k R (pgo + biiy

469 1 -~- 7 S9

part of an inch, is the space moved by the poiht c of thependulum when the penetration is completed.

Also t = — -A- : 4~ part of a second, is

2 h iiR V 1500. 643 r ’

the time of completing the penetration of 14 inches deep.

31. Upon the whole then it appears, that our rule willgive, without sensible error, the true velocity with which theball strikes the pendulum. But this is not, however, thesame velocity with which the ball issues from the mouth of thegun, which will be indeed something greater than the former,on account of the resistance of the air which the ball passesthrough in its way from the gun to the pendulum. Andthough this space of air be but small, and though the elas-tic fluid of the powder pursue and urge the ball for somedistance without the mouth of the piece, and so in somedegree counteracts the resistance of the air, yet it will beproper to enquire into the effect of this resistance, as itwill probably cause a difference between the velocity ofthe ball, as computed from the vibration of the pendulumand the vibration of the gun ; which difference will, by-the-by, be no bad ivay of measuring the resistance of the air,especially if the gun be placed at a good distance from thependulum ; for the vibration of the gun will measure thevelocity with which the ball issues from the mouth of it;and the vibration of the pendulum, the velocity with whichit is struck by the ball.