122 
MINUTES OF PROCEEDINGS OF 
calibre of gun, C' = diameter of shot. 7 and X are constants whose 
values have to be determined by experiment. The second term of the 
right-hand member of equation ( 7 ) represents the decrement in initial 
velocity due to windage, and the value of the coefficient X should be 
derived from a series of experiments expressly instituted for the pur¬ 
pose. Strictly speaking this value depends upon a great variety of 
conditions, but chiefly upon the strength and physical properties of 
the powder, and upon the length of the bore of the gun. Under 
normal circumstances, however, a mean value of X may, with but a 
very trifling error, be assumed, and General Didion, in his work 
above referred to, gives X = 2300 as the result of the French inves¬ 
tigations with the service gunpowder, but an analysis of the above 
experiments points to a considerably higher value. Indeed, from 
instances in these experiments, where the variation in windage was 
sufficiently great, 3158 has been obtained as the mean value of X, and 
as this number very nearly agrees with that stated by Colonel Boxer to 
result from the mean of Major Mordecai’s extensive experiments on 
windage, I have taken as correct the value of X, viz., 3200, given by 
that officer. 
Assuming X as above given, 7 is easily computed from the data 
furnished by experiment. 7 varies chiefly with the nature and con¬ 
dition of the powder employed, and the annexed table gives the values 
which have been obtained for the several guns experimented with, and 
the nature of the powder used in each case. 
Table II. 
Values of 7 for the under-mentioned Smooth bored Guns deduced from 
the Experiments recorded in Table I. 
Nature of Gnn. 
Nature of Powder. 
Value of 
7 
Nature of 
Gun. 
Nature of Powder. 
Value of 
7 
10 -inch gun - 
68 -pr. 95 cwt. 
Do. do. 
8 -inch gun, 65 cwt. 
32-pr. 58 cwt. 
L.G.W. A., 26/11/60 
L. G.W. A.,26/11/60 
L.G. Hall and Sons, 
22/11/60. 
L. G. Hall and Sons, 
22/11/60. 
L.G. W. A., 22/11/60 
3284’ 
3491* 
3536 * 
3307* 
3428* 
24-pr. 50 cwt. 
18-pr. 38 cwt. 
12 -pr. 18 cwt. 
9-pr. 13 cwt. 
6 -pr. 6 cwt. - 
12 -pr. Howr. 
24-pr. Howr. 
L. G. W. A., 26/11/60 - 
L. G. W. A., 25/11/60 
L. G. - - - 
L. G. ... 
L. G. ... 
L. G. ... 
L. G. ... 
3390* 
3454- 
3561* 
3422’ 
3321’ 
3291- 
3275* 
The experiments under discussion show that the equation— 
M C 2 —C' 
y = 7 . /—Tog.— — 3200 
m +7 
C 2 
( 8 ) 
gives the velocity due to a variation in the weight either of the 
charge or projectile with great exactness, the proper value of 7 being 
used in each series, and this equation has therefore been used to 
calculate the initial velocities of the various projectiles * thrown from 
smooth bored guns. 
These velocities may be depended upon as correct (supposing the 
same powder to be used) within very narrow limits, and the computed 
velocities are in this case perhaps preferable to direct determinations, 
as, unless the whole series for each gun were carried on at the same 
time, and with powder of exactly the same nature and date of manu¬ 
facture, discrepancies from variations in the strength of the powder 
would be sure to arise. 
* The mean weights and windages of the various projectiles have been taken. 
