THE USE OF FUZES.

324. All spherical shells, except those for the 24 and 12 pdr. howitzer, and all shrapnell, are fitted with the Navy time-fuze.

This fuze is composed of a composition driven in a paper case, and then inserted in a metal stock which screws into a bouching fitted to the shell.

The composition is covered with a safety-cap, which protects it from moisture and accidental ignition; also with a water-cap of peculiar construction, intended to protect the flame from being extinguished on ricochet.

A safety-plug at the lower extremity prevents the communication of fire to the powder in the shell, in the event of the accidental ignition of the fuze after being uncapped.

325. It is strictly forbidden to show or explain to foreigners or others the construction of any fuzes, except so far as may be necessary for the service of the guns.

326. These fuzes are of 3 1/2, 5, 7, 10, 15, and 20 seconds time of burning; which are supposed to offer a sufficient variety for most of the exigencies of service. There are also supplied paper-case fuzes of greater length, which, when used, are always to be inserted in metal stocks.

All the Navy time-fuzes—paper case as well as metal stock—being intended for use under a water-cap, burn a longer time in the open air.

All shells, unless otherwise ordered, are fitted and issued from the shell-houses with the 5-seconds fuze, which is to be regarded as the general working fuze.

For greater or less distances this fuze may be drawn, and any of the others substituted.

The Navy time-fuze is rarely extinguished by several ricochets on water; and near the end of its flight, when fired direct, frequently acts by concussion.

The fuze used should not be of longer time of burning than requisite to reach the object; the shorter times are of quicker composition, therefore more certain; also in firing on ricochet the shell may sink short of the distance necessary for its explosion, and consequently be supposed to fail.

327. For special firing, as for example at shore-batteries or masses of uncovered troops, any of these fuzes may be shortened. To do this, unscrew the water-cap and back the paper case out from the lower end with a drift and mallet; cut off from the lower end with a fine saw, or sharp knife struck with a mallet, the proportional part required, and insert the upper part in the stock, forcing it down with a few gentle blows with the drift; screw on the water-cap. It is preferable, however, when circumstances will admit, to take up such distance as will correspond with the time of flight of one of the regulation lengths. When firing against ships or earthworks, the fuze should be a little longer than necessary, in order to reach the object before bursting; but a little shorter when firing against boats or masses of troops, in order to insure its bursting in front of them.

328. The Bormann fuze is fitted to the 24-pdr. and 12-pdr. howitzer ammunition, and all shrapnell. It has also been fitted to certain shells used for special firing. The length of fuze is the limit of the distance within which this fire is effective.

This fuze is opened at the required number of seconds, by cutting close to the right of the mark on the index-plate. The cut should be made down to the plane of the table, in order to expose the composition; and is best made at two or three efforts, instead of trying to effect the cut at once. This fuze should be carefully explained to the men, as shells have been taken from guns with the cut made into the priming-magazine, which would explode them at the muzzle.

329. There are also on trial for the rifled cannon the percussion and time fuzes of Schenkl, Hotchkiss, Parrott, and others.

No reliable percussion or concussion-fuze has as yet been arranged for spherical shells.

330. These fuzes will be exhibited and explained by the Ordnance Officer on the application of Commanders of vessels, who, with the Executive Officer and Gunner, are enjoined to make themselves thoroughly acquainted with this most important part of the equipment.

331. Commanders of vessels will carefully note and report the efficiency of all fuzes fired in action or exercise; giving the elevation of the gun, the estimated or measured range, the number fired, the name of the inventor, whether percussion or time, the number of failures to explode the shell, premature explosions, and satisfactory action. Great waste of ammunition is frequently occasioned by an under-estimate of the distance.

332. The times of flight and length of fuze for all projectiles, so far as ascertained at the Experimental Battery at Washington, are given in the Table of Ranges, [Appendix B.]

333. The best effect of a percussion-fuze is obtained by firing into a mass of timber. They frequently fail if fired into a bank of soft earth, sand, or other material which does not offer a sufficiently sudden resistance; also, if fired at high angles of elevation, owing to the fact that the rifle-shells do not generally strike point foremost.

334. Time-fuzes are also very unreliable in rifle-guns; expanding projectiles cut off the flame from the fuze.

With the Parrott shell, however, the Navy time-fuze is the most certain of ignition and regular in its time of burning. The safety-plug should be removed when the Navy time-fuse is used in rifled cannon, as recent experiments show that it is a probable cause of premature explosions of shells.

In testing the Navy time-fuse by the watch, or michronometer, the safety-plug must be removed: otherwise the fuze will burn longer than the time for which it is marked.