82 
SHORT NOTES ON PROFESSIONAL SUBJECTS, 
80. Bashforth’s Chronograph. When a body moves in a straight line 
under the action of a force in the direction of its motion, which varies as the 
(velocity) 3 , a well known simple formula gives a relation between the velocities 
V and v at two points of the path of the body s feet apart. Professor Helie uses 
V V 
v = ^ ^ c j7 s > Iuse v =* i _j_ 26Fs 3 S0 ^ ° ne * s ° ot ^ er * 
The constants 25, or c, depend upon the form of the moving body, but they of 
necessity vary inversely as its weight. Bor similar forms of heads of projectiles 
it is usual to assume that the resistance varies directly as the section or as the 
(radius) 2 . In this case 5, or c, will vary as the (radius) 2 . On this supposition I 
shall be able to apply results obtained from the 12-pr. B.L. gun and 40-pr. M.L. 
gun to other calibres. 
In the trial experiment with my Chronograph with 121b. service shot, it was 
found that 25 = *000 000 084. (Report dated Dec. 18, 1865), and in the 
description of the Chronograph the value was more exactly given, 
5 = -000 000 0417.* 
Taking the shot at 12 lbs. and the radius = 1\ in. = *125 ft. we get, 
\2 pg 
•1257 x 7r 
RP 
= •000 064 jp, 
adapted for a shot of similar form, of radius R feet, and weight W lbs. 
Again, in Sept. 1866, some experiments were made with shot having heads of 
different forms, (1) hemispherical, (2) hemispheroidal, the diameters being nearly in 
the ratio 1 to 2, (3) ogival struck with a radius of one diameter, and (4) ogival struck 
with a radius of two diameters. In the report (Oct. 23, 1866), numerical values 
were given for 5fi, as stated below, where l = 150 feet, the distance between the 
screens. These values have been employed to adapt the results of these experiments 
to shot of similar forms but of different diameters and weights. 
Gun. 
Form of head. 
Weight of 
shot. 
Number of 
rounds. 
Value of 
IP. 
Value of 
2b or c. 
Date. 
lbs. 
12-pr. B.L... Service.. 
40-pr. M.L. £ Sphere. 
. £ Spheroid, . 
.. Ogival (1 diam.) 
... Ogival (2 diam.) 
12-00 
39-33 
21-81 
21-94 
11 
R2 
•000 064 jy 
Dec. 1865. 
5 
4 
10 
8 
•000 840 
•000 669 
•001 245 
•001 181 
R2 
•000 077 yjr 
R2 
•000 060 jp. 
R2 
•000 063 
R2 
•000 060 jp 
Oct. 1866. 
u 
II 
* See “ Proceedings,” R,A. Institution, Vol. V. p. 186, 
