STEEL AS APPLIED TO ARMOUR, 
231 
the hard face on which, is got by special treatment of only that part of 
the plate, and the so-called compound plates, on the Ellis and Wilson 
patents. The Ellis plates, as made at Messrs. Brownes, consist of a 
hard high carbon steel plate, welded to a foundation plate (previously 
prepared) of wrought-iron by pouring molten steel, lower in carbon 
and therefore softer, than the face-plate, in between the two ; the whole 
then being subjected to pressure by which the union is effected. 
I do not propose to notice any trials with plates on the Wilson 
patent, which is somewhat similar to the Ellis. Plates on the Ellis 
patent, as treated by a process invented by Captain Tressider, c.m.g. 
(late R.E.), of the firm of Messrs. J. Brown & Co., have recently 
been remarkably successful. The process by which these plates are 
“ Tressiderized ” is not yet public, but it is reported by some that it 
resembles the “ Harveyizing ” process, described presently. This, I 
think, is more than doubtful, for it would seem that if this was the 
process it would be attended with less risk to the plate if the hard-face 
plate was so treated before being united to its back—and, I understand, 
whatever the process is, it takes place on the complete “ compound 93 
plate. 
There are two ways that have been tried of getting a hard face on 
to what we will now call an all-steel plate. One is to heat up the plate 
and dip it to only a certain depth in oil, and thus harden the face. A 
plate so treated was taken by Schneider to Spezia in 1886, but it had 
warped very much. There does not seem to be any means of stopping 
this warping in this process; and though an isolated plate may stand 
its trial, a process which causes such malformations is, of course, 
inadmissible on the large scale. The most recent process is one pro¬ 
posed by a Mr. Harvey in the United States. In principle it is old, 
having been known for many years in Sheffield under the names of 
“case hardening” and “cementation.” It differs from these slightly, 
however, in its mode of effecting the desired result. A mild steel 
plate is covered with granular carbonaceous material well rammed 
down, and then placed in a fire-brick cell; this cell being then placed 
in a suitable furuace, the heat is raised to something over 2000°, 
which takes about two days. This heat is then maintained for about 
five days for a 10'5-inch plate ; the plate is then withdrawn and allowed 
to cool, covered with its carbonaceous material to prevent oxidation by 
the air. By these means the amount of carbon in the steel is increased 
by about one per cent, at the surface, the increase dying away as we 
get deeper into the plate. When the plate has cooled to a dull cherry 
red, or say about 1100°—1200°, it is suddenly chilled by a spray, and 
so further hardened. Special precautions are taken to prevent warp¬ 
ing, and I understand there is every promise of these precautions 
being eventually successful, though there is no definite information on 
this point yet. We will, now, briefly notice trials of a “ Tressiderized 99 
and a “ Harveyized ” plate. 
Trial of a Tressiderized plate at Shoeburyness on July, 23rd, 1891. 
This was a 7' 6" x 7' 6" x 10'5" plate. It was slightly warped by 
treatment, the face being convex. This was bolted to four feet of 
oak backing, the space between plate and backing, where former had 
