316 MESSRS. R. H. FOWLER, E. G. GALLOP, C. N. H. LOCK AND H. W. RICHMOND : 
Table III.—Mean Values of the Dynamical Constants of the Shells used, 
Determined before Firing. 
Types I., II. and III., Form A. 
Type IV., Form B. 
Type of shell. 
Length, 
inches. 
Weight, 
lb. 
Distance 
of centre 
of gravity 
from base, 
inches. 
Axial 
moment of 
inertia, A, 
lb. (in.) 2 . 
Transverse 
moment of 
inertia, B, 
lb. (in.) 2 . 
B/A. 
I. (Normal) . . 
11-53 
14-09 
4-727 
18-37 
143-9 
7-83(5) 
II. (Centre of 
gravity for¬ 
ward) 
11-53 
16-31 
5-124 
19-20 
165-0 
8-59 
III. (Centre of 
gravity back) 
11-53 
16-48 
4-203 
18-93 
129-5 
6-84 
IV. (Shells with 
pointed nose) 
13-15 
14-62 
4-965 
18-71 
166-2 
8-89 
and details of the groups fired are given in Table IV. The distance available 
between the firing point and the sea at Portsmouth is rather less than 600 feet. 
The motion of the shell was recorded over this range, within which the effects of 
gravity are fairly small and the path of the shell not widely different from a straight 
line. To achieve this the shell was fired through a series of millboard pistol targets, 
2 feet square, about -^o inch thick, which were fastened approximately at right angles 
to the path of the shell, at suitable distances from the muzzle .* The plane of the 
card was carefully adjusted, and it is probable that in no case did the angle between 
the path of the shell and the plane of the card differ from a right angle by as much 
as two degrees. As errors up to four degrees do not affect the shape and position of 
the hole in the card, which determine the position of the axis and the centre of 
gravity of the shell at the moment of impact, it may be assumed that in every case 
© 
* For the gun whose rifling made one complete turn in a length of 40 diameters of the bore (rifled 1 in 
40) ten cards were used, placed approximately at 60-foot intervals, the first card being 50 feet from the 
muzzle. For the gun rifled 1 in 30 twelve cards were used, the first seven being at 30-foot intervals and 
the later cards at 60-foot intervals as before. The distance of the cards from the muzzle of the gun was 
determined with a probable error of 1 inch. 
