280 
MEPPEN EXPERIMENTS. 
range. The plates were indifferently rolled, and contained some phos¬ 
phorus, it is said ; but the penetration of the shot was, after making all 
allowance, extraordinary. They were scarcely deformed in appearance 
when recovered. The steel was excellent. They had ogival points, the 
heads being struck with a radius of two diameters. This complete and 
easy penetration of 20 ins. of iron by the projectile of a 9‘45-in. gun is a 
striking feat. It may be instructive to analyse it. As a rule, we know 
the penetration which a projectile will effect, within very small limits, 
from its stored-up work and calibre. The length of the gun, 22’5 
calibres, with its charge of prismatic powder and initial velocity of 
1888 f.s. would naturally lead ns to expect a striking velocity of some¬ 
thing like that registered on this occasion, namely, 1876 ft., this, with 
the above projectile, would give 8499’7 ft. tons stored np-work and 
a penetration of 19‘31-ins. of iron. Colonel Inglis estimates that when 
7 ins. of iron is divided into two plates it loses 4 per cent, of the power 
of resistance it would possess if in a single plate. Probably 4 per cent, 
would be too large a deduction to make in the case of 20 ins. of iron 
being divided into two. Perhaps, however, we might consider that the 
19*31-ins. of calculated penetration of the shot in a single plate would be 
just about sufficient to give bare penetration of 20 ins. in two plates. 
How are we to account for the margin of power which carried the pro¬ 
jectiles 2000 metres up the range; it is difficult to say what this 
amounted to. It is to be regretted that the device, adopted at Spezia, 
of placing velocity screens on the far side of the shield was not employed 
on this occasion, as we should then have known exactly what force was 
actually expended in penetrating the structure. There can be little 
doubt however that it was a good deal less than we have accounted for 
above. As there is no magic in these matters we ought to be able to 
trace the result to its cause. Two possible causes are apparent; one 
that which we have noticed already, inferiority in the plate, the other 
special excellence in the form or material of the shot. Now the plate 
exhibited signs of bad welding. I am inclined to think that the actual 
form of the hole made by the passage of the shot in itself argued this. 
The back of a plate exhibits the process of yielding under the blow of 
a shot in the following way :—At a certain stage in 
penetration the plate opens at the back in a small 
star or cross opposite to the shots point. The 
corners thus formed bend back as the shot pro¬ 
ceeds, and, in a good plate, before the shot gets 
through, the corners are torn off along the dotted 
circular line, forming a rough hole of a diameter 
somewhat less than that of the projectile, which presses it out and 
and polishes it as it at length comes through. Now the Dillingen 
plate bent back and allowed the projectile to 
escape without tearing or shearing off these corners. 
This, I believe, argues bad welding, for as the plate 
approaches a laminated state the different layers 
acquire power to slide on each other and so 
accommodate themselves to the bend required to 
let the projectile pass through—just as it is easy 
to bend up the corner of a thin book remote from 
