had evidently been thoroughly broken up. In the large official photograph a trace of white radiating lines is visible, and these always imply extreme disintegration, being the mark of langrage skimming over the plate face. There are no cracks.

On 10th November, 1899, a firing trial of one of John Brown and Co.'s armour plates was made at the proving grounds of Armstrong,

Whitworth and Co., Limited, selected by Captain Mörch from a lot manufactured for the armour of two Norwegian battle-ships building in Elswick shipyard. The sample was subsequently reduced to dimensions for the prescribed test, of which the conditions were as follows:-Plate 8 feet by 6 feet by 5.9 inches; backing, 24 inches oak and 1-inch skin plate; bolts, eight of 2 inches diameter; number of rounds, four;

projectiles, steel armour-piercing 6 inches diameter and 100 lbs. weight; striking velocity, 1,960 feet per second; striking energy, 2,664 foot

tons: calculated perforation, 134 inches of iron. The plate was expected to resist this attack without being perforated or seriously cracked (see Figs. 3 and 4).

The projectiles provided by the Norwegian authorities were made at the Elswick Works on the Wheeler-Stirling process, and, as they weighed

FIG. 1. G-IN. ARMOUR PLATE FOR THE NORWEGIAN NAVY.

102 lbs. each, the specified velocity was reduced to 1,936 foot-seconds, to compensate for the extra weight. The striking energy thus remained

unaltered at 2,664 foot-tons, and the calculated perforation remained 13·4 inches of iron.

The four prescribed rounds having been easily defeated, and no cracks being developed in the plate, the trial was pronounced highly satisfactory, and the whole of the armour represented was approved. To obtain some idea, however, of the ultimate defensive power of the armour, the attack was supplemented by two extra rounds at increased velocities, which also failed either to perforate or to produce any cracks in the plate except a few superficial air lines on the face. The following are the particulars of the results of each round: --

All projectiles were smashed to pieces. Except in the case of the

first round, exact measurement of

penetration was prevented by fragments of shot lodged in the indent. The last round was capable of piercing 17 inches of wrought-iron by Tresidder's formula; that is, 27 times the thickness of the plate fired at.

There is one interesting feature in this trial to be noticed, namely, that the bulge made at the back by No. 4 round has in its centre a starshaped tear, showing that the shot is in a measure boring a hole which would be completed by sector-shaped pieces being torn and displaced outwards from the shot point. In the other five rounds apparently boring has been wholly defeated, and the shot point so far flattened as to be compelled to punch out a disc to get through the plate, entailing as already pointed out much more energy. It may be seen that No. 4 round happened to have less energy than all except No. 1; and it may be concluded that its perforation would be completed with less work than any of the other rounds. It is, in fact, an example of the case above referred to, where the blow is so truly normal to the plate surface and the projectile so good that the point, instead of being broken, retains much of its sharpness. Probably a capped shot would behave very nearly like this No. 4 projectile. If plates were really struck nearly normally on service, as may be seen here, caps should certainly be adopted.

A rough idea of the relative powers of armour of different kinds is important. I have always believed that the best plan of achieving this is to take wrought-iron as the standard. Captain Tresidder has suggested

Shot's point apparently not destroyed. The above constituted the acceptance test.

a "figure of merit" based on the equivalent of each plate in wroughtiron thus expressed. Ordinary steel was equal to one and a quarter, Harveyized steel to from two to two and a half, and Krupp process to from about two and a half to three times its thickness in wrought-iron. Some manufacturers urge that steel can be made more uniform and certain in its quality than wrought-iron; but who is to fix the steel selected? Wrought-iron seems much less arbitrary, and less liable to be misunderstood, and the scope of its variation is but small.

The following table shows figures of merit attained by various Krupp process plates-that is, the relation of the thickness of wrought-iron that would have been perforated, to the thickness of the actual Krupp process plate attacked.

To pass on to actual use. At the present time the armour that has, I think, assumed by far the greatest importance is 6-inch plating. This comes in the following way. Six-inch plate lends itself to face-hardening specially well; thinner plates are apt to be contorted or warped in the hardening process. On the other hand, plates are always more difficult to make as the thickness increases. Now it happens that 6-inch Harvey and Krupp process armour had been successfully made considerably before other thicknesses. It also happens that Sir William White has given our battle-ships 6-inch protection for their 6-inch Q.F. guns, while those of foreign Powers long had 3, 4, 5, and in only, I think, one single instance, 6-inch armour. Consequently, our designs at once lent themselves to the adoption of hard-faced armour, the opportunity was promptly used, and, consequently, for a considerable period, extending nearly to the present time, our Q.F. guns have been singularly well protected; for while it would be a great advantage to have 6-inch plates against an adversary's 5, 4, or 3-inch of the same kind, the difference is greatly increased when our 6-inch are face-treated and those of other Powers are untreated steel. The special importance consists in the fact that the armour is so related to the power of the usual Q.F. guns, that while we could perforate their sides and nearly all cases with armourpiercing shells, they could not perforate ours, even with shot. Most naval officers depend more on the fire of their heavy Q.F. batteries than "record" plate.

An early