prescribed, a supplementary test shall be made by firing the third shot under the same conditions as the first two shot; if this passes the test as prescribed above, the lot shall be accepted; if it fails to do this, the lot shall not be accepted.

3 Weight uncapped.

For intermediate thickness the velocity shall be determined by interpolation.

(b) Armor-piercing shell. Two capped shell, sandloaded to standard weight, shall be fired against a hard-faced Harveyized armor plate secure to a timber backing in a manner satisfactory to the Chief of Ordnance, of 3-inches thickness for 5-inch and 6-inch shell, 4-inches for 8-inch shell, 5-inches for 10-inch shell, and 6-inches for 12-inch shell, with a velocity 4 of about 1,420 f.s. for the 5-inch shell, 1,220 f.s. for the 6-inch shell and 920 f.s. for the 8-inch, 10-inch and 12-inch shell at impact, with the requirement that the shell shall go through the plate unbroken, and then be in a condition for effective bursting.

4 The weight of powder charge to give the prescribed velocity will be determined shortly before the test, cast iron projectiles of proper weight being fired for the purpose; this weight of charge will be taken as giving the prescribed velocity to the projectiles undergoing test.

(c) 12-inch deck piercing shell. Two shell, sandfilled to standard weight, will be fired with a striking velocity sufficient to pass completely through a 4½-inch nickel-steel protective-deck plate inclined so as to give an angle of impact of 60 degrees, and to be supported by a suitable backing of wood; or both shell shall be subjected to such alternate ballistic test as the Department may judge to be an equivalent to the above in its effect upon the projectile.

The nickel-steel protective-deck plate shall be manufactured by the open-hearth process and shall contain about 3¼ per cent of nickel, not more than six one-hundredths of one per cent of phosphorous; not more than four one-hundredths of one per cent of sulphur, shall be the best composition in all respects.

It shall be oil or water tempered and annealed, and the whole plate shall be subjected to the same treatment at the same time.

Tensile test will be made after final treatment. One longitudinal specimen for tensile test will be taken from each plate. Each shall show a tensile strength of at least 80,000 pounds per square inch and an elongation in 2 inches of at least 27 per cent.

Bending tests will be made as follows: A piece cut from the plate shall be doubled cold around a curve of which the diameter is not more than the thickness of the piece tested without showing any cracks. The ends of the piece are to be parallel after bending. These specimens shall be 12 inches long, 1½ inches wide, and 1 inch thick.

At the discretion of the inspector, bending specimens ½ inch square taken with a hollow drill, may be substituted. Such specimens must bend cold to 180 degrees flat, without sign of fracture on outer surface.

(d) 12-inch Torpedo Shell. Two shell, sandloaded to standard weight, will be fired from a gun or mortar into a sand butt with a pressure in the powder chamber of about 37,000 pounds per square inch to test structural ability.

If the shell are found not seriously deformed by discharge from the piece and in a condition for effective bursting, the lot will be accepted.

If any of the shell fail to pass this test, the lot will be rejected.

The following extract from the "Circulars and Specifications of the Navy Department concerning Armor Plate and Appurtenances for Vessels of the U.S. Navy," (April 22, 1907) while pertaining to another subject, will be pardoned if introduced here for the purpose of demonstrating the seemingly paradoxical requirements a manufacturer is called upon to meet:

(Par. 60.) The ballistic test for acceptance of armor shall be made as strictly as practicable in accordance with the following tables, the Department reserving the right to use guns of other calibres than designated for any plate if it is deemed advisable.

In the test of armor of Class A there shall be three impacts with striking velocities as given in the following table, capped armor-piercing projectiles being used: