beyond the back, and that without de veloping the sign of a crack. This plate showed the same amount of homogeneit y as the steel one. but was tougher and more tenacious. as was shown by the grip ping of the projectiles. The metal did not come to the front in fringes. but el ipped off about the edges of the shot hob's. Much of the energy was expended in breaking up the projectiles, the locali zation of effect was very remarkable. At the lest shot at the all-steel plate the 8-in.
projectile succeeded in getting its point only 5•f3 in. beyond the beck. The plate, though, cracked in two cross-lines, which were so serrated that. when the plate was removed from its backing. the parts re mained firmly in place. (See Fig. 4.) The principle upon which compound armor is bused is generally thought to lie a good one, as hard projectile-breaking face and a graduated resisting back.
Great efforts will probably continue to be made to harden the face of plates mail the getting through of the projectiles is no longer a possibility. Several methods for applying this principle to armor plates by processes resulting in superfi cial carbonization have been devised, and among them is that now known as the Harvey process. Each plate is treated with the design of transforming its sur face into it high grade of steel. without causing its back to lose any Ilf its original toughness. and without producing a pronounced plane of demarkation be tween the two qualities of metal. Plates treated by this process were subjected to trials at • Annapolis, twenty-one shots from a Hotchkiss 6-pounder being fired at a 8-in, plate of nickel steel. Only three penetrated more than half an inch. and all projectiles were smashed. By far the most momentous question which the Navy Department in this country has had to consider in connection with the construction of the new navy is that of armor: first, to se cure a supply of American manufacture ; and, secondly, to determine what kind of armor should be adopted, having reference both to its composition and mode of treatment. The series of tests already referred to resulted in the decision to adopt nickel steel. It remained, however, to give a thorough trial to the first armor of domestic manufacture before beginning to place it upon the vessels, and for this purpose it was decided to order typical plates to test (I) whether our domestic manufacturers could produce an armor that would stand competition with foreign material, and (2) which of the various modes of treatment would give the best results.
Six plates were furnished and set up at Indian Head (1891). and they were subjected to tests than had ever been applied to foreign government trials. Four shots were fired at each plate with a 6-in. gun, with an impact velocity of 2,075 ft. per second, using the Holtzer projectile of 100 lbs. One shot was then fired at the center of each plate from an 8 in. gun, with :in impact of 4,088 foot-tons, or 2,000 in excess of the 6-in., using Firming and
Carpenter projectiles of 210 and 2.50 lbs. weight, respectively. the plates being normal to the line of fire. Three of the plates were furnished by the Bethlehem Iron Co. and three by Car negie, Phipps & Co., sonic being rolled, others forged, and several being treated by the _Harvey process.
The results of the trial were in the, highest degree satisfactory. Each of the six plates manufaetured in this country was superior to the English compound plate, while the nickel I1r•ccyer1 plate and the high-carbon nickel plate were superior to all the foreign plates of the Annapolis trial. They may, therefore, be pronounced in advance of the best armor hitherto manufactured in Europe. Further light was thrown upon the question of the relative merits of all-steel and nickel-steel armor, and any doubt which may have remained upon that subject was finally set at rest. Of the three plates made at Bethlehem two were of nickel steel, one treated by the Harvey process, the other not, and the third was of all steel, Ilarveyed. Both the nickel plates proved to be far superior to the all-steel Ihtrveyed plate, not withstanding the advantages which it may have derived from the Special treatment : and both proved supe rior to the French all-steel plate tried at Annapolis. A third nickel plate. manufaetured by C'an•negie, under the 'Idling, process, also showed a marked superiority over the all-steel plate of this year, and both it and the corresponding Ilet hlehem plate manufactured tinder the hammer showed a capacity of resistance to perforation fully 10 per cent greater than that of the French all-steel plate. In this respect the results furnished Ly the two American plates manufactured by the different processes (forging and rolling) proved to be remarkably uni form, the 0-in. shots that were fired at them differing in penetration but an inappreciable amount. The trial thus definitely establishes the fact that armor of excellent finality may be produced by"the rolling process, and that forging by means of the hammer, the greatest source hitherto of expense in mannfactnre, is no longer to be regarded as an absolute necessity. The importance of this fact can hardly be overestimated, for it raises a probability that within a year or two the arno•-prodneing eninwity of the United States inay he in ease of necessity, and that if we had 10,000 tons to let, and could give eighteen months from date of contract to commence delivery, the coat of manufacture would he reduced from 25 to 33 per cent, while the work hitherto confined to two firms would be thrown open to a large number of comitetitos. Finally, the trial shows that the high-carbon nickel Ilarveyed plate is un doubtedly the best arnor-plate ever subjected to ballistic test.