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O. N. Rood on Elongated Projectiles. 19 
turn in 5 feet, it is plain that at the moment of leaving the muz- 
zle, the ball will be revolving at the rate of 200 times per second. 
To ascertain then the initial velocity, I constructed two ballis- 
tic pendulums, similar to those used by Robins. The tota 
ot ae £1 21°75 ; 20°2 Ib. 
or the pendulum resisted the impact of a body in motion as 
though its weight had been only 20:2 Ib.- The axis was made 
of a bar of steel, two sides of which were ground to an edge. 
Instead of the ribbon used by Robins to measure the chords, 
a narrow strip of paper was employed, which was fastened to 
one side of the pendulum on a line with its centre, that is 39°7 
inches from the axis. 
The smaller pendulum was similar in construction : its weight 
was 7833 grs., it made 93 oscillations in one minute, consequently 
its centre of oscillation was 16°29 inches distant from the axis; 
the centre of the pendulum and its centre of gravity were is- 
tant from the axis 16-6 and 152 inches; it resisted therefore as 
though its weight had been 7038'4 grains. « Be 
For barrel No. 4 I succeeded in constructing, after many trials 
a ball or picket, on the American model, Fig. 2, whose 2. 
ight was accurate up to 500 yards; its dimensions 
Ball No. 4. 
Length 62 in. Diameter ‘37 in. Length in diameters, 167. Weight 113°34 grains. 
[aa NS 70s | cone he Figen, 1 Oh | ee 
| 520 fit. A ee ee ee. . 
Ee: t nit | Ag ¢ 2 2 
691 “« 20 3 1 1 
691 « bats ee 2 2 
691 165 “ 8 
849 « “ z l 4 
849 «& bois 165 * 2 1 2 
965 “ | 244 “ 8 6 3 
16 
1128 “ | 285:8 (1500 “ Flight accurate. 
