CO 
ARMOUR AND ITS ATTACK BY ORDNANCE. 
to this at the time. Taking 1 2 it altogether, however, the result was 
better than any hitherto achieved, except some obtained with special 
plates which have now to be noticed. These so far rival them that it 
is difficult to judge between their respective merits. 
Tresidder ^he P^ es i n question were the result of a hardening process devised 
plates, by Captain Tresidder, late B.E., who had joined the Atlas Works of 
Messrs. Brown. The process mainly consists in the application of jets 
of cold water distributed by means of pipes over the face of an Ellis 
plate. The jets being projected forcibly cause cold water to come 
in contact with the hot metal in a way which is impossible in plunging 
a hot plate into water, owing to the steam generated at the surface 
which prevents true contact. There are other features connected with 
TresiddeEs process, such as a system of gauging to enable allowance 
to be made for contortion, which is necessary to cause the finished 
plate to be of the required form to fit the ship*s side ; the main point, 
however, is the application of cold water jets. During the year 1891 
several trials were made of portions cut from the same rolled plate, 
some oil-hardened and some hardened on Tresidder*s process. 1 The 
results yielded by the latter were excellent, forged steel projectiles of 
Hadfield’s manufacture breaking up like chilled-iron shot, the white 
splashes radiating from the point of impact such as had hitherto been 
seen only with chilled shot. 3 
On October 8rd. took place, on board the Nettle, a trial very similar 
to the series at Shoeburyness, but which is to be preferred as an 
example seeing that it was made in conformity with the regular estab¬ 
lished Nettle conditions. The projectiles were three 6-inch shot 
of Holtzer’s forged steel, weighing 100 lbs. each, and two of Palliser 
chilled-iron. The velocity was about 1976 f.s., the charge being 48 lbs. 
EXE powder. The energy w r as 2708 foot-tons, and calculated per¬ 
foration 12*57 inches of iron or 10*1 inches of steel. The plate was 
8 feet x 6 feet x 10*5 inches. Figs. 9, 10, and 11, pp. 61,62, and 68, 
show the front and back and edge view of the plate after the trial. 
Bounds Nos. I. and IV., steel and chilled-iron respectively, produced 
less effect than II. and III., also steel and chilled-iron respectively, 
the lower half of the plate being apparently harder than the upper. 
All are completely broken up. A supporting structure would suffer 
very little from any yielding that has occurred in this plate. 
It may be seen that the Tresidder plate was less severely tried than 
the Harvey plate last noticed. It also suffered less, so that no strict 
comparison can be made. 
Cammeii ail Messrs. Cammell submitted an all steel plate for trial at Portsmouth 
Bte ^ettie! e> about this time, but while highly satisfied with the results they did not 
consider it superior to the compound plates. 
Nickel steel plates, made at St. Chamond, also about this time gave 
good results as to toughness, but a plate 1*58 inches thick attacked by 
1 See “Engineer,” November 6 h and November 13th, 1891.—In case of a slightly contorted 
plate concrete was run in between plate and backing to give support. 
2 An experienced naval officer actually assumed from the appearance of the plate that ch lied 
shot had been employed, and previous experience fully justified him in doing so. The author has 
acted on the same sign hitherto, which can no longer be depended on. 
