-- 406 
very serious cracking, this enormous “ punishment”’ 
having been sustained by an area of 48 square feet only. 
Most of the trials made against steel-faced armour have 
been against plates from Io to 12 inches in thickness. 
For thicknesses up to 12 inches it is probably within the 
truth to say that for zovmal zmpact the steel-faced plates 
of recent manufacture have been equal in their resistance 
to perforation to iron plates 25 to 30 per cent. thicker and 
heavier. For oblique impact the hard armour is probably 
still more superior to iron, glancing the projectiles at 
angles of obliquity when they would have “ bitten” into 
the iron. A few experiments have been made in this 
country and abroad on much thicker steel-faced plates, 
ranging up to 18 or 19 inches in thickness, and of these the 
most recent and important are the trials made at Spezia 
in November, 1882. Three targets were constructed for 
these trials, the armour plate on each being nearly 11 feet 
long, 84 feet wide, and 19 inches thick. One of the targets 
was covered by a steel-faced plate made by Messrs. 
Cammell, another by a steel-faced plate made by Messrs. 
Brown, and the third by a steel plate made at Creusot. 
All three plates were similarly backed and supported by 
4 feet of oak; the Creusot plate was fastened by no 
less than 20 bolts, and the Sheffield plates had only 6 
bolts each. Against these targets the roo-ton muzzle- 
loading gun was brought into action. At first the powder- 
charge used (329 lbs.) was that which gave such a 
velocity to the chilled cast-iron projectiles—zooo Ibs. in 
weight—as would have perforated a 19-inch iron armour 
plate. The actual penetrations were from 3} to 5 inches 
in the steel-faced plates, and 8} inches in the steel plate, 
showing that the actual superiority of all the plates over 
jron considerably exceeded the estimate. The steel plate 
did not crack at the first shot: the steel-faced plates did, 
_ but not to any serious extent. Next followed a more 
severe attack, the powder charge being increased to 
480 Ibs., giving the projectiles a velocity estimated to be 
capable of perforating about 24 inches of iron armour. 
The total energy of the projectile moving at this velocity 
exceeded 33,000 foot-tons. All the plates were broken 
into pieces by this terrific blow. The steel plate was 
split into six pieces, but the numerous bolts held these 
pieces in position, and still preserved the defensive power 
of the target. Each of the steel-faced plates was broken 
into five pieces, and on account of the fewness of the 
bolts these pieces fell to the ground, leaving the targets 
uncovered. The whole of the chilled cast-iron shots 
were broken up on impact, and the penetration into the 
steel-faced plates was less than that in the steel plate. 
At this stage the comparative tests ended. A third round 
was fired, with the heavier charge and a steel projectile 
against the steel plate. The shot was stopped, the pene- 
tration was only 7 inches, but the plate was broken up, 
and the -backing seriously splintered. A fourth round 
was fired at this target and completely wrecked it. 
On a review of all the circumstances of the experi- 
ments, it must be admitted that the greatest success was 
attained by the steel plate, although this must be attri- 
buted rather to the number and excellence of its fasten- 
ings than to superiority in quality of the plate over the 
steel-faced plates. The latter proved themselves less 
penetrable than the steel plate, and had rather the advan- 
tage as regards fracture at the end of the first two series 
NATURE 
[March 1, 1883 
of rounds; but they were insufficiently secured. One 
definite lesson to be learned from these experiments is, 
therefore, that a larger number of bolts is needed for a 
given area of steel or steel-faced armour than has been 
commonly used. Another lesson taught by these trials 
is that the steel armour plates of Creusot manufacture in 
1882 are far superior to those made six years earlier. It 
is not at all probable that light guns such as broke the 
22-inch steel plate to pieces in 1876 would have been 
equally effective against the 19-inch plate recently tested. 
In both cases the plates were made specially for the 
firing tests, and they may not have been ‘‘ merchantable 
articles’’ in the sense of representing large quantities of 
steel armour. But nevertheless this 19-inch plate shows 
what can be done with steel, if cost is of secondary im- 
portance. Authoritative statements are wanting of the 
actual processes of manufacture, or of the cost of produc- 
tion. It is reported that the 19-inch plate was hammered 
down from an ingot three or four times as thick as the 
finished plate, and that the face was oil tempered. If 
this is correct the cost must be high, and probably as 
great as, if not greater than, that of steel-faced plates. 
Moreover if such an amount of “work” has to be put 
into steel plates in their conversion from ingots into the 
finished forms, then no great economy or advantage can 
result from the power which the maker has to cast steel 
ingots in special shapes or sectional forms. The Creusot 
Company use a soft steel containing perhaps three-tenths 
to four-tenths per cent. of carbon, give it toughness by 
means of a large amount of hammering, and harden the 
face by oil tempering. On the contrary, the Sheffield 
firms, as the result of numerous experiments, use a hard 
steel for the face, the percentage of carbon amounting to 
about twice that in the Creusot plate, and support this 
by a tough iron back. With this hard steel, oil tempering 
does not appear to be beneficial, although with softer 
steel it undoubtedly is an advantage. These steel-faced 
plates which were tested at Spezia were really samples 
of large quantities made at Sheffield in the same manner. 
Probably equally good results would have been obtained 
if any one of the batch of plates represented had been 
selected for test. In this respect, therefore, there is a 
marked difference between the test to which the two 
manufactures were subjected. 
As between the steel and steel-faced plates tried at 
Spezia we may assume that there is no notable difference 
in resistance to perforation or to fracture. Possibly, with 
equally good and equally numerous fastenings the steel- 
faced plates would have had some slight advantage, and 
in other trials mentioned later on steel-faced plates 
have had a decided advantage. Supposing no important 
difference to exist, then the choice between the two kinds 
of armour will be governed by their relative prices; and 
how these compare, we have no means of judging, but it 
seems probable that the steel-faced plates would be at 
least as cheap as steel plates made in the manner 
described above for the steel test-plate. 
It may be convenient in this connection to briefly 
describe the mode of manufacture of steel-faced plates. 
Messrs. Cammell prefer to pour the molten steel on to 
the face of a wrought-iron plate which has been brought 
to a good welding heat. The layer of molten steel is 
} surrounded by a frame of wrought-iron which has 
