580 GUNNERY. 
Initial Ve- Weight) inital] of the gun or piece from which they have been dis- B 
‘locities of | Nature of the Guns. | Kind of Powder. jof Pow: ‘Velo- 6 Sa a} We shall now proceed to consider the ef 4 
Projectiles. der. -| city. | fects which are produced by the resistance of the air; “ 
avr and we shall again-have occasion ‘to admire the a. 
A musket with al ( Fine war powder, 7 |.1390.| Jay address with which Mr Robins has ‘investigated th 
bore 1ft. 10 inch. } Eoin do. 7 .|.1367 | branch of the subject. sake ab Sa baa 
long _| | Firework do. 7 1372. . The resistance opposed to a body moving in a me= 
Fine war powder, 7 | 1956 | dium of unifom density was always.considered by phi- 
‘|Rifled carabine _|.4.Fowling do. 7 | 1920 | Josophers as proportional to the square of the velocity ; 
Firework do. -7 | 1934 | that is, if a ball moved with four times the velocity in 
A wall-piece carry-| ( Fine war powder} 20 | 1956 | one part of its path that it did in another, the resistance — 
ing a leaden bul-| 4 Fowling do. 20 | 1928 | tothe greater velocity would be 16 times as great. Now, 
let2Joz.in weight] { Firework do, 20 | 1923 | if we take’a ball 4 of an inch in diameter, moving with 
A musket with .al- a velocity of 1600 feet in a second, “it will be found, 
bore $ ft. 6 inch, } Fin war powder} °7 | 1736 | from theory, (see Newton’s Principia, Prop. 38.), that 
long ¢ its resistance will be 44. pounds avoirdupois, the wei 
f of water being taken to that of air as 850 to 1. r 
In order to ascertain the effect produced by a diffe- In order to compare this result with experiment, 
rence in the weight of shot, and in the windage, three My Robins-used his ballistic pendulum, with which he 
‘ bullets were fired from a al sr and-two from the ould easily measure the velocity of a projectile at any 
‘musket 3 feet 6 inches in length of bore. point of its:path. He charset a muha barrel three 
times in succession with a leaden ball } of an inch in 
‘Quantity off Initial | diameter, and with about half its weight of powder, 
Weight of Balls. _| fine War | Veloci-| and fired it against the pendulum at 25, 76, and 125 
Powder. | ties | feet citanee oe the mouth of the piece respectively. 
The following were.the results : 
-—— 
al 3} oz. 7 ‘123 drams| 1770 
Wall-piece ; 3 123 1855 ; ; 
“plece 4 37. butof thesame di Distance from} Tract of air | Velocityin | 
: _ ameter as the first‘ball|23 2068 the Mine, Senet Eee s 
- 1 02. 7 1736 Pon KAP R ‘Gt 
Musket .22 7 1834 ; 50 focod, 
} Carabine®ball. 7 1863 * ; — 
The following experiments were made in a mean state = e a 
-of the atmosphere, to shew how the initial velocities va- 
ry with different charges of fine war powder : Hence, in passing through 50 feet of air, the bullet 
lost a velocity of 120 or 125 feet per second ; and as it 
passed through that space in ., or 4, of a second, the 
Weight of Powder in drams.|Initial Velocities. medium quantity of resistance must have been about 
120 times the weight of the bal, or 10.1b. avoirdupois, 
Musket with af® ae since the ball weighed", of a pound. It follows, there- 
hore 3-ft- 6a 73 fore, that the theoretical is to the observed resistance 
10 1984 as 4: to 10, 04 ‘ } Ly 
Wall-piece with ae bees . _The following results were obtained with the same 
a.bullet. 24 oz. 25 2060 piece: ; 
; Distance from the piece. , Pinte 
The following results were obtained with four Medium o i 1690. 
muskets of different lengths. The ball was 1 oz. in ss eaaaridee loyal three trials : pire ; 
weight, and the charge was seven drains of -fine war é Medium of 1 
. powder : 175 “\°4s"a, tel. eee i 300 
: Length of Barrel from Initial» | In this experiment, the ball lost a velocity of 390 feet 
_| the Ball to the Muzzle. | Velocities... in a second, in traversing 150 feet of air; and the ve- 
locity computed from these data is 11 and 12 lbs, avoir« 
Feet. Inches. dupois, even greater than before. 
o i 1037 The following experiments were made in smaller ve« 
1 10 1390 locities. The same barrel, and balls of the same size, 
j : Hes “but less powder, were now used. 
Distance from the piece. Velocity. 
Medium of 7 ,, 
Abin ty. $i tee Ta five tral piso a 
‘On the mmuicteimids* A Projectiles in a resisting 250 Be eee et {Revue f 950 " . 
“Medium. es ° 
The ball, ‘therefore, in passing through 925 feet of 
, Hrraerto we have covsidered only the state of pro- air, lost a velocity of 230 feet in a ae ans it 
jectiles immediately after they have quitted the mouth — passed through that space in vgths of a second, the ree - 
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