106 
ARMOUR AND ITS ATTACK BY ORDNANCE. 
closely at about 1580 feet velocity. At lower velocities the English 
formulae give greater perforation than the foreign, and at higher velo¬ 
cities the French formula of De Marre gives the highest result, that 
of Krupp comes next, and last the English, as shown in the table 
below calculated for the 6-inch 100 lb. projectile. 
Perforation through wrought-iron in inches. 
Striking at Striking at Striking at 
Formula. 1000 feet. 1680 feet. 2400 feet. 
Fairbairn. 5*92 9*88 15*26 
Maitland . 5*87 9*72 15*26 
J. de Marre.. 5*01 10T3 19 25 
Krupp. 4*94 9*82 18*89 
At higher velocities matters are still worse, the calculated perforation 
for the projectile, weighing 28*7 lbs., fired by Canet from a 10 cm 
(3‘94-inch) gun, 80-calibres long, on September 20th, 1892, with a 
muzzle velocity of 3366 f.s., would be by De Marre 20*2 inches, and by 
the English formulae less than 14*5 inches. 
With a view to test the formulae at high velocities, the Ordnance 
Committee, on July 20th, 1892, fired a 6-inch Holtzer forged steel 
projectile, with a striking velocity of 2378 f.s., at a target made up of 
two thicknesses of wrought-iron (12 inches + 5 inches), that is, 17 
inches in all. By Fairbairn*s formula this projectile should not per¬ 
forate over 16 inches in two plates. By De Marre* it should pass clean 
* The formuloe here employed are those communicated by Lieut. Perry, U.S. 
Artillery, viz. :— 
1 
w v 
De Marre’s ... i 0 ' 61 = --—. 
log" 1 2 9616 D 4 
A wv<i 
Krupp s ... t - = - \ 
log- 1 5*7776 
Where t = thickness of wrought-iron perforated in inches. 
w — weight of projectile in lbs. 
v = striking velocity in feet. 
D = diameter or calibre in inches. 
through the plate, with a remaining velocity exceeding 1000 f.s. and 
by Krupp*s about 890 f.s. On this occasion the shot actually per¬ 
forated, and passed on for 1600 yards. Velocity screens had been 
erected behind the target. There was some uncertainty in the record 
owing to the flying off of a piece of iron from the target, but from 
screen and calculation as to graze, the remaining velocity appears to 
have been between 560 and 690 f.s. 
Subsequently on November 15th, 1892, two rounds were fired from 
the 4*7-inch gun with 45-lb. shot, with a striking velocity of about 
2217 f.s., both projectiles, however, broke up. They were not Holtzer’s 
make, and there was some evidence that they were not flying truly; 
nevertheless, it appears that great excellence is required in projectiles 
striking even wrought-iron at a very high velocity, for their full cal¬ 
culated perforation to be realised. 
(To be Continued). 
