March 1, 1883] 
NATURE 
407 
previously been attached to the iron plate; and it is 
pressed against the surface of the iron plate by a cover 
carried by an hydraulic ram, until the welding is complete 
and the steel has solidified. Messrs. Brown prefer first 
to roll a steel face-plate as well as an iron back-plate, 
and then to raise both to a welding heat; the molten steel 
is afterwards poured into a space left between the two, 
and hydraulic pressure is applied until the solidification 
has taken place. The remaining processes are similar 
in the practice of both firms. After welding has been 
completed, the whole mass is reheated and rolled down 
to the finished thickness of the armour plate. The steel 
face is usually about one-half the thickness of the iron 
back, and it is a curious fact that the iron and steel 
maintain their relative thicknesses as the rolling pro- 
ceeds, even when the reduction in thickness during 
rolling is very considerable. This reduction varies from 
one-half for thin armour-plates, up to ro or 11 inches in 
finished thickness, to one-third with 18 to 20 inches of 
finished thickness. Some competent authorities consider 
that too little work is done in the rolls on the thicker 
plates, but there is a need for further experiment to 
show whether this viewis correct. Whatever may be the 
cause, it would seem that the best results so far have 
been obtained with steel-faced plates below 12 inches in 
thickness. 
Simultaneously with the Spezia experiments another 
competition was proceeding, near St. Petersburg, between 
steel-faced and steel armour. The plates tested were 12 
inches thick, 8 feet long, and 7 feet wide. They were first 
fired at with the 11-inch breech-loading gun, throwing a 
550-lb. chilled cast-iron projectile, with a powder charge 
of 132 lbs. The velocity of the shot was 1500 feet per 
second. Messrs. Schneider supplied the steel plate, 
which was fastened with twelve bolts. Messrs. Cammell 
made the steel-faced plate, which had only four bolts in 
it. The first blow on the steel plate broke it into five 
pieces ; the projectile was destroyed, but it penetrated 13 
inches into the target. A blow of equal energy on the 
steel-faced plate produced only a few unimportant cracks 
in the steel, and the penetration was about 5 inches only. 
Three out of the four bolts were, however, broken. A 
second shot was then fired at each plate with 81 lbs. 
charge. The steel plate was broken into nine pieces, and 
the penetration was 16 inches : whereas on the steel-faced 
plate the principal effect produced was to break the only 
remaining bolt and to let the plate fall to the ground, face 
downwards. The back of this plate was perfect, and the 
target behind the plate was uninjured. In this trial the 
steel-faced plate proved greatly superior to the steel, but 
had insufficient fastenings. It is proposed to increase 
the bolts in number, re-erect the plate, and continue the 
trial, of which the further results cannot fail to be 
interesting. 
This contest between steel and steel-faced armour must 
not be allowed to withdraw attention from the great 
superiority of both, in certain respects, to iron armour, 
Even as matters stand, either of these modern defences 
is greatly to be preferred to their predecessor. Against 
this hard armour chilled cast-iron projectiles break up in 
a manner never seen with soft iron. Projectiles of this 
kind are virtually impotent, and must be replaced by 
more expensive, harder projectiles, if steel or steel-faced 
armour is to be attacked. Even with steel projectiles 
results cannot be obtained such as were possible with 
iron armour. Perforation of armour by shells carrying 
relatively large bursting charges is no longer a possi- 
bility : and the heaviest gun yet made cannot drive its 
projectiles through a thickness of hard armour only 
three-fourths as great as the thickness of iron which it 
it could perforate. 
The use of steel and steel-faced armour will involve 
many experiments to determine not merely what descrip- 
tions of projectiles are best adapted to damage or 
penetrate it, but what are the laws of the resistance of 
such armour to penetration and disintegration. All the 
formulze based on experiments with soft iron armour and 
chilled cast-iron projectiles are inapplicable under the 
new conditions. Perforation is no longer to be feared as 
the most serious damage likely to happen to armour 
plates: more moderate thicknesses of hard armour suf- 
fice to stop the projectiles from the heaviest guns than 
would have been considered possible a short time ago. 
Instead of perforating 19 inches of steel or steel-faced 
armour, the projectile of the 1oo-ton gun with a given 
velocity only penetrates 8 inches into the plates. But, on 
the other hand, the possible disintegration and fracture 
of the armour plates are becoming important matters. 
Makers of armour plates have to endeavour to produce 
materials which shall resist fracture as well as penetra- 
tion, and the only proof of their success or failure is to 
be found in the results of actual trials. Experiments are 
equally essential to progress in the manufacture of guns 
and projectiles. The example set by Italy must be 
followed; the necessary experiments must be on a large 
and costly scale, and they may lead to many departures 
from former practice. But if real progress is to be made 
in the armour and armament of ships, it must be prefaced 
by experiments beside which those of the former Iron 
Plate Committee will appear insignificant. 
In conclusion it may be stated that although iron armour 
has been practically superseded for the sides and batteries 
of war ships, it is still preferred for decks. Experiments 
have shown that for angles of incidence below 20 degrees, 
and for such thicknesses—not exceeding 3 or 4 inches 
—as are used on decks, good wrought-iron is superior 
to both steel and steel-faced plating. The explanation 
of this departure from the laws which hold good for 
thicker plates and greater angles of incidence cannot 
be given here, but the fact has been established by 
elaborate trials made in this country and abroad. 
SMOKE ABATEMENT 
Report of the Committee of the Smoke Abatement Exhi- 
dition. (London: Smith & Elder, 1883.) 
HIS volume, which has just been issued, presents 
many points of interest, as it is the outcome of the 
labours of a Committee formed in 1881 with a view to 
ascertain what means could be adopted to check the 
growing evils arising from the evolution of smoke which 
attends the combustion. of bituminous coal. It may be 
said to be the continuation of work undertaken by the 
several Parliamentary Committees which met in 1819, 
1843, and in 1845. In the previous efforts attention 
appears to have been mainly directed to lessening the 
