164 
MINUTES OE PROCEEDINGS OE 
The objections to this mode of experimenting are numerous and self- 
evident. As the weight of the ball is increased, the vibration and shock 
caused in the pendulum must give rise to large errors. With the increased 
distance, there is the difficulty of striking the pendulum so that there may 
be no impulse on the axis of suspension, and no tendency to twist about a 
vertical axis. Further, as experiments have been commonly made, the shot 
were not removed from the receiver until a certain number of rounds had 
been fired, and thus the positions of the centre of gravity and centre of per¬ 
cussion were in a state of constant variation. There was also the uncertainty 
arising from the necessity for assuming that the average initial velocities were 
the same for the same charge and ball for different distances of the receiver. 
The large guns now made cannot be experimented on with the ballistic 
pendulum in the ordinary way. 
I have been particular in referring to dates in what precedes, because 
M. Didion's Traite de Balistique is our standard work on the subject. The 
theory of the edition of 1861 is practically the same as that of 1848, 
depending, not only upon the same law of the resistance of the air, but 
upon the same numerical formula of resistance. The tables to facilitate the 
practical application of the theory are also, to all intents, the same. We 
must therefore date this theory 1848, before the Crimean war, and before 
the introduction of rifled ordnance and projectiles of a cylindrical form. It 
is true that M. Didion does make some slight reference to small elongated 
projectiles, diameter Om.119 (4*7 in.) and length 0m.240 (9*4 in.) for he 
remarks, “ On reviendra, section ix., sur les resistances de divers genres que 
rair fait eprouver aux balles oblongues; mais en attendant que des expe¬ 
riences plus precises aient fourni des resultats plus certains , nous 
admettrons pour les balles oblongues.^leines et pour les boulets oblongs, 
un coefficient de resistance egal aux deux tiers de celui de la balle spherique, 
e'est-a-dire ^ = 0*081 et p'=0*018 (1 + 0*0028?;); il en sera les trois- 
quarts pour les balles creuses, comme celle du modele 1859, e'est-a-dire 
egal a 0*020. On adoptera, pour les boulets oblongs de campagne et de 
siege, le meme coefficient ^4= O’OIS.” 1 It is plain, however, that the 
resistance of the air to elongated shot depends greatly upon the form of the 
shot, and that something far more precise than the above is required. 
It is remarkable that Hutton concluded from Ins experiments that, for 
every 100 feet added to the velocity of a shot, there was an increasing 
addition made to the resistance of the air up to a velocity between 1600 f.s. 
and 1700 f.s., where it attained a maximum. Thus, in his table of the air's 
resistance to a ball of 2 inches in diameter, we find 3 
vel. f.s. 
Resistance 
in oz. 
1300 
683*3 
1400 
811*5 
1500 
947*1 
1600 
1086*9 
1700 
1228*4 
1800 
1368*6 
1900 
1505*7 
2000 
1637*8 
Ai 
+ 128*2 
+ 135*6 
+ 139*8 
+ 141*5 
+ 1.40*2 
+ 137*1 
+ 132*1 
a 2 
+ 7*4 
+ 4*2 
+ 1*7 
—1*3 
—3*1 
— 5*0 
1 Didion, Traite, p. 74, 1861. 
2 Hutton, Tract 37, p. 218. 
