400 
MINUTES OF PROCEEDINGS OF 
“Engineer,” 1867, January 4th, 11th, 18th, and 25th), I would ask 
you to observe the beauty of the effect of the inelastic medium water on 
the lower side pressing against the bottom and superincumbent mass, 
and on the upper side lifted in a wave, as shown in fig. 
I conclude the ricochet will be repeated until the difference of the 
pressures caused by the resistance of the water against the lower half 
and upper half of the anterior surface of the projectile, which is a 
function of its velocity, becomes less than the vertical downward com¬ 
ponent of the shot. 
To return to armour, it may be observed that the power of turning 
in instead of glancing off point first when striking on armour at an 
oblique angle increases with the radius of the circle with which the 
ogival head is described, inasmuch as the limiting angle of penetration 
is approximate to that made by the tangent to the ogival curve at the 
apex with the axis of the projectile, i.e. } the limiting angle of pene¬ 
tration with ogivals of various radii may be said to be approximately 
as follows :— 
For 1 diameter . 60° 
n H // 53° 8' 
v li // 48° 12' 
Captain Nolle on Complete Penetration of Armour Plates . 
In a report on the experiments relative to the penetration of armour 
plates by steel shot, printed in 1866, Captain W. H. Noble, It.A., 
discusses the means that exist of comparing the thickness of armour up 
to 4J ins. of plate, pierced by various projectiles, and also of calculating 
the probable effect that may be expected from any projectile. He 
WV 2 
shows that the formula —^— which he expresses in “ foot tons,” gives 
the “ work ” done by the shot on striking very correctly, whether of a 
light projectile with a high velocity, or a heavy one with a low velocity ; 
further, he considers that penetration is in inverse proportion to the 
circumference of the shot. 
It must be observed that the calculation only applies to the question 
of complete perforation, when the plate may be supposed to be sheared 
along the line corresponding to the circumference of the projectile. 
This would be most nearly correct in the case of flat-headed shot. 
To conclude with something more practical; Captain Noble considers, 
speaking roughly, that at 200 yds., 7-inch, 8-inch, and 9-inch projectiles 
may be expected to penetrate armour plates whose thickness does not 
exceed their respective diameters by more than lin.; i.e., the 7-inch 
may pierce 8-inch armour, the 8-inch may pierce 9-inch armour, and 
the 9-inch shot, armour lOins. thick. The powers of projectiles of 
larger calibre are less thoroughly tried, but they appear to correspond 
generally to those of the smaller ones. 
Following naturally on such matters comes the question as to the 
manner in which fire may be directed on a vessel in action with best 
effect. 
