O. N. Rood on Elongated Projectiles. 21 
Ht The initial velocity in Jacobs’ rifle, judging from his state- 
ments, must be about 986 feet: as the twist is one turn in 28 
inches, the ball makes 422 revolutions per second. 
| Now why not, it is often asked, project either of these balls 
with an initial velocity of 1600 or 1700 feet per second? Sim- 
ly because the above rates of revolution then become wholly 
insufficient. ‘T'o test this point, I constructed for barre] No. 2 a 
ball weighing 136 grains and only 2°08 diameters in length, con- 
mo get not requiring as rapid a rotary motion as the Swiss 
Ball 2:08 diameters in length. 
Initial Velocity. No. of Rev. Distance. 
1716 ft. 486 165 ft. All sidewise. 
It would probably require a rate of at least 600 revolutions 
r second, and the Swiss ball being again much longer would 
rdly fail to need a rate of from 700 to 800. 
; The twist of Whitworth’s rifle (ball 3 diameters long) makes 
One turn in 20 inches: its initial velocity is not given, though it 
| is understood to be greater than that of the Enfield: # it be as 
high as 1600 feet, the rate of revolution of the projectile will be 
960 times in a second; if 1700 feet, 1020! 
_ The above mentioned experiment will perhaps suffice to estab- 
lish the fact that for any given projectile, the necessary rate of 
= increases rapidly with the augmentation of the initial 
velocity. 
The inability to use larger charges of powder prevented me 
from pursuing the investigation farther in this direction, eae it 
| 
| 
| 
to 
examine whether at very low velocities the necessary rates of 
revolution for projectiles 2 and 24 diameters long rapidly de- 
creased. An elongated ball for barrel No. 5 was now 
length; weight 208 grains. ‘The initial velocity was determined 
with the smaller oudoliad and found to be 232°6 feet : the veloc- 
a was determined also from the time of its flight: a distance 
15-41 feet gave it 233: the average of 14 shots at 442 feet 
- Made it 216, 
Ball 1-9 diameters in length, weight 20°8 grains. 
‘ aa Wai ama es ; 775 ft. Flight accurate, 
Another ball was now constructed for this barrel; the results 
were as follows: 
Ball 2:3 diameters in length, weight 265 grains. 
Be op ot ge hae ion. 75 ft. Flight accurate. 
20 
A third ball, 3 diameters in length, was finally made for the same 
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