THE EOYAL ARTILLERY INSTITUTION. 
65 
THE QUESTION OE THE DAT, 
OR 
“IKON-PLATES” versus “GUNS.” 
By W. H. NOBLE, M.A., Lieut. E.A. 
ASSOCIATE MEMBER, ORDNANCE SELECT COMMITTEE. 
1. The actual "work done” at the moment of impact,, by two projectiles 
of different weights and animated with different velocities may be taken as 
comparatively proportional to the vis viva of each. 
This is not, strictly speaking, quite correct, as some force is expended in 
altering the shape of the different shot when they strike. 
Upon a projectile striking a rigid and immovable object, like an iron 
target, a certain alteration of figure is experienced by the shot; but the 
difference between the forces required to produce this effect in different shot 
is so inconsiderable that it may practically be neglected, and the "work done” 
may be stated, as above, to vary as Wv 2 , W being the weight of the shot, 
and v its velocity at the moment of impact. 
The work done, at 200 yds. distance, by the 110-pr. Armstrong rifled gun, 
with 14 lbs. charge, where W= 111 lbs. and #=1178 ft., and the 68-pr. 
smooth-bore gun, with 16 lbs. charge, where JU=66 lbs. and #=1422 ft., is 
in favour of the former gun in the proportion of 11*5 to 10, nearly; but we 
find that the penetration is in favour of the smooth-bore 68-pr. Again, at 
the same distance, the 110-pr. firing a bolt of 200 lbs. with a charge of 
10 lbs., where ^=200 lbs. and #=780 ft., in comparison with the 68-pr. 
as before, will be as 10 to 11, nearly, the 68-pr. thus, having a slight 
advantage; yet the penetration of the 68-pr. is far greater, that of the 200 lbs. 
bolt being almost nothing. 
2. How comes it then, that although the "work done” by each shot 
varies so little, the penetrations shew such a marked difference ? I think 
that the following explanations will throw a light on the subject:— 
The actual "work done” by each shot is, as we have seen, nearly the same; 
but one does its work in much less time than the other . This explains the 
whole matter. 
The 200 lbs. bolt, with a low velocity , stikes a heavy blow on a spot in the 
target, but it takes a certain length of time to accomplish that blow; so 
that, during this interval, all the surrounding particles of iron have ample 
time to sustain the point struck; the force of the blow is thus spread over 
a large surface of the target, and the cohesion of the particles is undisturbed, 
[vol. hi.] 10 
