NOTES UPON THE MANUAL EXERCISE.
FOURTH COMMAND.
"SERVE VENT AND SPONGE!"
"The Gun Captain-serves, then stops the vent!"
256. A difference of opinion being entertained among artillerists with regard to the utility of stopping the vent, the continuance of the practice, as directed in the text, is recommended.
The thumbstall has been made of various materials, but its use is somewhat inconvenient for the Gun Captain, and he cannot feel that the vent is stopped. At the Experimental Battery of the Ordnance Yard the naked thumb is used, and experience shows that the gun is never so hot as to occasion the least inconvenience, except with howitzers.
257. It has been the uniform practice at the Experimental Battery at the Ordnance Yard, Washington, and also on board the Gunnery Ship Plymouth, in 1857-'58, to use a moist sponge; and as no accident from premature explosion has taken place in either case, the inference is that the method is a safe one, and might obviate other precautions, especially where reloading is necessary, as in firing salutes, when, there being no shot over the cartridge, it is imperfectly consumed.
258. "Strikes the staff several smart taps under the muzzle!" to shake off any adhering fragments of the cartridge. Should any burning fragments be drawn out, the Loader extinguishes them with the wet swab; the Gun Captain again commands "Sponge."
259. Gun Captain "serves the vent with his priming-wire!" If at any time he should find the vent obstructed, and be unable to clear it with the priming-wire or boring-bit, he will at once report to the officer of division, who will order the vent-punch used; or, if this should fail, have recourse to the vent-drill and brace in charge of the Quarter Gunner. The boring-bit, vent-punch, and drills should be used with caution, as, being of steel, they are liable to be broken off in the vent and thus effectually spike the gun. After clearing the vent the bore should be sponged.
260. Spongers and Loaders are to be careful to keep their bodies as much within the port as practicable, otherwise at close quarters they will be picked off by musketry.
FIFTH COMMAND.
"LOAD!"
"No. 3 removes cap from fuze!"[36]
261. The cap is never to be removed until the shell has been entered in the gun. With high elevations, or when rolling, care should be taken that the shell does not slip down the bore before this is done.
The cap or patch is removed by taking hold of the lug with the forefinger and thumb, first raising it a little, and without twisting; a pull readily removes it. The patch is passed to the Gun Captain, as an evidence that the priming has been exposed; the patches to be preserved and accounted for at the end of the firing.
262. The Loader must be careful not to touch the fuze composition with his fingers, for fear of injuring it by moisture. Where the firing is not hurried it is advisable to raise the priming of the fuze, to insure its ignition. All of these details should be carefully explained to the crew.
263. No wad is required over a shell, but a selvagee wad may be used in heavy rolling.
264. When loading with shot a selvagee wad is placed over it. A part—half or a third—of a selvagee wad, is equally efficient in holding the shot in place.
265. Shells should be used against Ships at all distances where the penetration would be sufficient to lodge them. They are of no service in breaching solid stone walls, but are very effective against earthworks, ordinary buildings, and for bombarding. For these purposes a good percussion or concussion fuze is desirable, but no reliable fuzes of these kinds have as yet been devised.
266. Solid shot should only be used when great accuracy, at very long range, and penetration are required.
267. If, in loading, a shot or shell jams in the bore, no attempt should be made to force it down, but it should be withdrawn. This may be done with the ladle, by depressing and striking the muzzle against the lower sill of the port, or by running the gun out hard against the side at extreme depression.
268. A gun is not to be loaded with more than a single shot at once, without the express sanction of the Captain, and never with more than a single shell. Solid shot are not to be fired from shell-guns without a direct order from the Captain.
269. Experiments show that firing two loaded shells together should never be practised. With quite reduced charges [of from 1/8th to 1/12th the weight of the single shell], of 88 loaded shells thus fired, 25 were broken and 48 did not explode, and some of the remainder were exploded too soon by the shock of discharge. Of 50 unloaded 8-inch shells, fired two at the same time, with 6 lbs. of powder, only one was broken by the shock of the discharge. This difference between loaded and empty shells is accounted for by the fact that a small hole is generally broken into the outer shell, through which its charge is ignited. See p. 13, Report of Admiral Farragut, dated August 31, 1853, on experiments made at Old Point Comfort.
270. In loading with a shell, the most exact attention is required to all the precautions relating to the position of the fuze and the mode of setting home the shell. The Loader is to be specially instructed that unless the leaden patch is stripped off, to expose the priming, the fuze will not ignite, and consequently the shell cannot explode.
271. Grape-shot have not sufficient penetration to be used with effect, generally, against ships-of-war beyond 150 yards. When the men on the spar-decks of the enemy are exposed, by the heeling of the ship, grape or canister may be used against them, at distances varying from 200 to 300 yards. Against light vessels, a single stand of grape from heavy guns may be used at about 400 yards. The dispersion of the balls is about one-tenth the distance, and is practically independent of the charge.
272. The XI-inch gun, at 10° elevation, gives for the mass of grape or canister a range of about 1,300 yards; the spread about 10°. They may therefore be used with great effect against boats or exposed bodies of men.
273. A stand of grape is not to be used with any other projectile.
274. Canister or case-shot, prepared for immediate use, are supplied for all guns, including boat and field howitzers, and are effective at short distances against boats or exposed bodies of men; they may be used also, under favorable circumstances, against the tops of an enemy.
275. Shrapnel-shell or spherical case-shot is intended to exceed the range of canister, and is to be used only under the same circumstances, but at an increased distance. Canister is more effective at from 250 yards with the 12-pdr. howitzer, to 400 yards with the XI-inch; but beyond those distances shrapnel should be used up to 900 yards for the 12-pdr., and 1,500 with the XI-inch. A well-delivered shrapnel-shell from a heavy gun must sweep away the crew of a pivot or other gun, on a spar-deck not protected by bulwarks. The 'distant firing' charge is always to be used with shrapnel.
SEVENTH COMMAND.
"PRIME!"
"He inserts a primer and turns the hammer down upon it."
276. To prevent the primer from being blown out of the vent by the blast of the next gun, as occasionally happens on light-covered decks.
With guns of the old pattern this cannot be done, because, if turned down, it would interfere with the aim.
277. It is essential that the head of the primer shall be placed flat and pressed close upon the vent, that the hammer may strike it fairly. The tip of shellac, by which the lower end of the tube is sealed, occasionally obstructs the jet of flame so as to split the tube. In this case the flame is dispersed laterally, and fails to ignite the charge; it is therefore a good precaution to pinch the end of the tube before putting it into the vent.[37]
278. The tubes of all the primers are carefully gauged before issuing them for service; but such as, from any cause, become so much enlarged as not to go easily into the vent, should be rejected without attempting to force them down.
It will occasionally happen, either from carelessness or inattention to the instructions given for the proper manner of pulling the lock-string, that the head of the primer will be crushed without exploding it. Frequently a second and stronger pull will have the desired effect, if the fulminate has not been dispersed; in case, however, this attempt should prove unsuccessful, the tube of the primer should be drawn out, if possible, before using the priming-wire to clear the vent.
279. In case either lock or primer should entirely fail, recourse will be had to the friction-primers or to the spur-tubes. In using the first, the Captain of the gun, after taking the primer from the box, will raise up the twisted wire-loop until it is on a line with the spur; place the tube in the vent with the spur towards the muzzle of the gun, and so that this spur will rest on the lock-piece; then hook the lanyard into the raised loop, and pull it, when otherwise ready to fire the gun, as though it were a lock-string, using, however, a less degree of force. The lanyard may be hooked to the loop before the tube is put into the vent. When the spur-tubes are used, the Gun Captain exposes the priming and the 2d Captain applies the match.
280. The men should be practised at unloaded guns, in placing the primers, both percussion and friction, properly, and in pulling the lock-string so as to insure their explosion, until this very essential knowledge and skill have been perfectly attained.
EIGHTH COMMAND.
"POINT!"
"His eye ranging over the sights!"
281. The Gun Captain gives the necessary order, "Right" or "Left," "Raise" or "Lower," by voice or sign. He alone should speak, giving his orders in a sharp, clear tone, but not louder than necessary for his own crew to hear him.
282. He should make use of the following signs to assist in making himself understood, which, when the crew become well drilled, are sufficient without the verbal orders.
In Pointing.—He should move the left hand, held vertically, to the right or left, according as he wishes the right or left tackle hauled upon.
In Elevating.—He should move the hand, held horizontally, up or down, according as he wishes the breech raised or lowered.
283. Officers of divisions, while instructing the men in aiming, should be particular in impressing upon their minds the necessity of bringing the eye to an exact level with the bottom of the sight-notch, as otherwise they will fire too high.
284. In lateral training, when the direction of the gun is frequently changed by the coming up or falling off of the ship, or when the position of the object to be fired at is rapidly changing by passing in opposite directions, or from other causes, it is better to train a little beyond, and then watch the proper moment for firing, instead of endeavoring to train at once directly on the object.
285. The lateral training, or pointing, when considerable, should always precede the elevation; because, the jarring of the gun is apt to alter the elevation.
286. "If roller handspike is not used in training." A great difference of opinion exists on this point. The use of the roller handspike somewhat facilitates extreme train, but the gun cannot be fired until it is unshipped, which alters the elevation and consumes time. It is perhaps preferable to use one handspike under the bracket, manned by two men, and the other to lift and slue the gun, manned by one man, under the transom.
287. "Elevate or Depress as directed!" If the carriage is fitted with a quoin, handspikemen standing between the handspikes and the side of the ship, place their handspikes on the steps of the carriage and raise the breech. As soon as the quoin is free, the 2d Captain takes hold of it with both hands and withdraws the quoin to the full extent; handspikemen "raise" or "lower" the gun slowly and steadily. When the proper elevation is given, the Gun Captain gives the word "Well!" and the 2d Captain forces the quoin tight under the breech, giving the word "Down!"
288. To facilitate the operation of pointing guns according to the distance of the object aimed at, sights are prepared and fitted to each gun; and breast-sweeps for all truck-carriages of heavy guns.
The ordinary sights consist of two pieces of bronze gun-metal, one of which, called the reinforce-sight, is a fixed point, firmly secured to the sight-mass, upon the upper surface of the gun between the trunnions. The heads of the sights should not be bright, otherwise it interferes with the aim when they are exposed to a bright sun.
289. The other, or breech-sight, is a square bar or stem, with a head, in the top of which is a sight-notch. It is set diagonally, so as to expose two faces to the rear; the rear angle chamfered, to afford a bearing for the clamp-screw. This bar or stem is made to slide in a vertical plane, in the sight-box fixed to the breech sight-mass, and is held at the various elevations for which it is graduated by means of a thumb-screw. Its length is sufficient for all the elevation which can be given—about 5°—before the muzzle appears above the front sight, after which a long wooden sight must be used, graduated for the whole length of the gun, using the notch in the muzzle.
The bar or stem of the sight has lines across its faces denoting for all the old guns degrees of elevation, each of which is marked with the number of yards at which a shot or shell will strike the point aimed at, when that line is brought to a level with the top of the sight-box, and the gun is loaded with a specified charge of powder; for the guns of the new system, the ranges are marked in even hundreds of yards.
The uppermost line on the stem marked level is the zero of the other graduations, and when adjusted to the level of the top of the sight-box, the bottom of the notch in the head of the breech-sight and the apex of the reinforce-sight show the dispart of the gun. When the line of sight coincides with these points, it is parallel to the bore, and when continued to a distant horizon, the gun is laid level or horizontal.
Sights should invariably be made so that the level line on the stem will correspond with the bottom of the head when it rests on the sight-box, and thus secure a dispart-sight in case of accident to the screw in the sight-box.
A white line, one-fourth (.25) of an inch wide, drawn on top of the gun from the breech-sight to the notch on the swell of the muzzle, has been found to greatly facilitate the aim. For night-firing a broad wooden block, painted dead-white, to ship over the reinforce-sight, leaving 1/4 of an inch of the sight exposed, will assist in preventing the aim from being too high.
290. For shot-guns the ranges in yards for one shot with the distant-firing charge of powder are marked for each degree of elevation on the right in-board face of the sight-bar; for the ordinary firing, on the left face.
291. The gun being placed a certain height above the water, depending on the class of vessel and the deck on which it is mounted, it is evident that, when the axis of the bore is horizontal, the shot will have a range proportionate to this height. This range or distance is commonly called point-blank, or point-blank range, and is the number noted in the column marked P.B., or 0°, or level in range tables.
This point-blank, therefore, depends on the class of gun, the charge, and the height above the water.
292. A preferable definition of this distance is "range at level."
293. The aim is always supposed to be directed at the water-line. But, with the sight-bar at level, if a gun is aimed by it at the water-line of a vessel at point-blank range, the shot would strike short of the point aimed at by about one-quarter of the distance; or, if aimed, under similar conditions, at the upper part of the hull, the shot would fall a distance below the point aimed at equal to the height of the gun.
294. In firing at small objects, particularly boats, within point-blank range, it is therefore important to attend to this source of error. It is desirable that all sights should be marked, from 100 yards to the greatest range, and thus avoid all consideration of point-blank.
In fitting new guns, or those upon which the sights require replacing, the sight-bar will be fitted as described in Article 289, and graduated from 100 yards downwards.
For shell-guns the ranges are marked for shells on the sight-bars, in the same manner as those for the shot of shot-guns.
295. These sights being each adjusted to a particular gun, and marked with its class and number, do not, in strictness, admit of being transferred to other guns, even of the same class.
296. When used, the stem of the breech-sight must be raised or lowered, to correspond with the ascertained or estimated distance, in yards, of the object aimed at, and firmly secured there by the thumb-screw. Then, if the ship be steady, elevate or depress the gun until the line of sight from the bottom of the notch of the breech-sight, the top of the reinforce-sight, and the point to be struck, will coincide; but if the ship have a rolling motion the gun must be so laid, after the sight is set for the distance, that this coincidence may be obtained, if possible, at the most favorable part of every roll which the ship makes.
297. The inclination of the line of metal to the axis of the bore varies in guns of the same class, as well as in those of different classes. Aiming, therefore, by the line of metal cannot be relied on for definite ranges; besides that, within those ranges, it is apt to mislead by giving too much elevation to the piece. Therefore, when the established sights are not furnished, or have become unserviceable, wooden dispart-sights lashed on the reinforce should be immediately substituted. A narrow groove in the upper surface of the wooden sight, made to coincide with the plane of the line of sight marked on the gun, will assist the Gun Captain in getting the true direction quickly.
Half the difference between the diameters of the gun at the base-ring and swell of the muzzle, or at any intermediate point on the line of metal, will give the proper height of the dispart-sight at the point where the least diameter was taken, to which must be added the height of the lock-piece above the base-ring, in order to get a line of sight over it, parallel to the axis of the bore.
The guns of the Dahlgren pattern are cylindrical for a certain distance forward of the base-line, always giving a line of sight parallel to the axis of the bore.
298. All the new guns are marked on the top of the lock-piece, base-ring, the reinforce sight-mass, and the swell of the muzzle, by notches which indicate a vertical plane passing through the axis of the bore, at right angles to the axis of the trunnions.
299. Pivot-guns have been supplied with trunnion-sights, designed to be used when the ordinary sights do not give the required elevation. This instrument, however, gives but a rude approximation in either elevation or direction.
300. The rifled cannon in service have the breech-sight on the side of the breech and the front sight on the rimbase, which permits the gun to be accurately aimed and the object kept in view at all elevations. It is intended in future to apply this arrangement to all cannon mounted on pivot-carriages.
301. Various modes have been practised to ascertain at sea the distance from the object aimed at, so as to regulate the elevation of guns, but none can be depended upon for giving it with minute accuracy, and even when obtained it is continually varying; therefore, when the projectile is seen to exceed or fall short of the object considerably, the sight-bar must be readjusted accordingly. It thus becomes, under ordinary circumstances, the best instrument for approximating distances. In correcting the elevation, however, the variation of range to the first graze, attributable to eccentricity, differences of windage, and other causes, must be taken into consideration, as, under the most favorable circumstances, at the Experimental Battery of the Ordnance Yard, this variation is found to equal fifty yards, more or less.
302. In addition to the errors arising from these sources, we have also those due to the direction and force of the wind, the movement of the ship across the line of fire, and to sheering round a pivot when performing evolutions.
303. They can be obviated or diminished by the following means:
1st. Allow the Gun Captain to estimate the distance to windward or to leeward, right or left, to be allowed for the deflection; or,
2d. Indicate the number of yards right or left of the object; which, after all, depends on his estimation of distance.
3d. Furnish a sight which, in addition to the elevation, allows for the deviation, and permits the Gun Captain in all cases to aim directly at the target.
Such a sight is furnished to the Parrott rifles, and is desirable for all guns.
304. In case the ordinary sights should be lost or rendered useless, tangent firing may be resorted to against ships, by pointing with the wooden dispart-sight at such part of the ship as the Tables indicate for the distance, and according to the class of gun in use at the time.
A Table of this kind is appended, which has been calculated for the 8-inch and some of the heavier of the 32-pounder guns when loaded with single shot and distant-firing charges.
The different classes of sailing ships-of-war, whether of the same or of different nations, are not of the same length, nor are their masts of the same height from the deck, or from the water. They, however, correspond so nearly, for the same class of ships of the same nation, that calculations made from the angles subtended by the average height of their masts, will generally give their distance with sufficient accuracy for general firing.
Tables are inserted at the end of the book, in which the distances corresponding to different angles made by the masts of English and French ships-of-war are shown—from which the intermediate distances due to other angles may be estimated, and the sights regulated accordingly, if circumstances should render it desirable. Also an abridged Table, in which the height of our own mast is used as the base.
305. Officers of divisions and Captains of guns should be occasionally practised in measuring the distances of objects by the eye, at times when opportunities offer of verifying the accuracy of their estimate by comparing it with the distance obtained by the foregoing methods, or any other which will afford the best means of comparison.
306. Within point-blank range, if the hull of an enemy's vessel is obscured by smoke or darkness, the aim may be directed by the flashes of his guns.
307. Most naval guns are now fitted with elevating screws, passing through a hole in the cascabel of the Dahlgren system, and for those of the old system attached to the carriage: but the ordinary beds and quoins are also still in use; they are arranged to allow the extreme elevation and depression of the guns which the ports will admit with safety. When the inner or thick end of the quoin is fair with the end of the bed in place, the gun is level in the carriage; or horizontal, when the ship is upright. The degrees of elevation above this level, which may be given to the gun by drawing out the quoin when laid on its base, are marked on the side or edge, and those of depression on the flat part of the quoin, so that when the quoin is turned on its side for depressing, the marks may be seen. The level mark on the quoin is to correspond with the end of the bed. When the quoin is entirely removed, and the breech of the gun rests on the bed, the gun has its greatest safe elevation; and when the quoin is pushed home on its side, the gun has the greatest safe depression that the port will admit.
Care must be taken that the stop on the quoin is always properly lodged, to prevent the quoin from flying out or changing its position, and that the bed is secured to the bed-bolt.
Porter's bed and quoin has been adopted for all carriages requiring quoins. This quoin, being graduated to whole degrees, requires a small additional quoin for slight differences of elevation in smooth water.
When the elevating screw is used, a quoin should be at hand to place under the breech of the gun, when at extreme elevation, to relieve the screw from the shock of the discharge, and prevent a change of the elevation, as well as to take the place of the screw if it should be disabled. When the fire is continuous at the same distance, the lever of the elevating screw should be secured by a lanyard, to prevent the screw from turning and altering the elevation.
308. If a greater elevation for broadside-guns should be desired for any special purpose, it may be obtained by placing inclined planes behind the rear trucks, for them to recoil over and produce a corresponding depression of the muzzle of the gun as it comes within the port. But it will be observed that, beyond the elevation which the ports will admit of, the sights can no longer be taken by the tangent or any other top sight, as the upper sill of the port interferes. The gun must therefore be laid by the quoin and pendulum.
Additional depression may also be obtained by placing inclined planes for the front trucks to recoil upon, or by raising the breech by means of a wooden toggle placed vertically under it. One end of a tripping-line is fastened to the middle of the toggle, and the other to the breeching-bolt in the side of the ship; by this arrangement the toggle is tripped from its place at the commencement of the recoil, and the muzzle is raised so as to clear the port-sill by the preponderance of the breech.
NINTH COMMAND.
"READY—FIRE!"
"Waits patiently for the coincidence of the sights upon the object."
309. The exact moment for firing, at sea, necessarily varies with circumstances; but when these are favorable the following general principles should govern:
310. When the ship is steady, the gun should be fired when the line of sight is brought upon the object; but when the ship has much rolling motion, the moment for firing should be chosen a little before, so that the shot will probably leave the gun when the roll brings the line of sight upon the object aimed at.
When practicable, and too much time will not be lost, it will be best to fire when the vessel is on the top of a wave and just begins to roll towards the object. If the loss of time should be found objectionable, the gun may be fired at any other instant, when properly pointed, giving a preference, however, to the moment when rolling towards rather than when rolling from the object, and making due allowance for the probable change of elevation by the roll of the ship before the shot leaves the gun.
311. If, from any cause, the firing should be delayed after the gun has been pointed, it should be carefully pointed again before the order to fire is given.
312. The great object is to fire low enough to strike the hull if the shot preserve the intended direction, and as a general rule to strike it near the water-line.
313. To avoid loss of shot from lateral deviations, it is recommended to direct all the guns to be pointed to strike somewhere between the fore and mizzen masts of an enemy; when quite near, the guns of the forward divisions should be pointed in preference to that part of the hull about the foremast, and one or two of the after guns at the rudder, if it should be fairly exposed.
REMARKS ON THE DIFFERENT KINDS OF FIRING.
314. Firing at Will.—By this is meant firing the guns independently of each other, each Captain of a gun seizing the most favorable opportunity. This firing should always be used in action—unless ordered to the contrary—whenever the object is visible, the smoke from one gun not greatly impeding the firing of another.
315. Firing in Succession.—By this is meant firing one gun after another in regular order, commencing from the foremost or after gun, according as the wind is blowing from aft or forward. This firing may be used with advantage in the commencement of an action, or whenever a continuous, steady fire is desired, as the smoke from one gun will not impede the firing of the next.
316. Quick Firing.—By this is meant rapid firing at will, the tangent-sight not being raised. This firing should be used only when close alongside an enemy, as then but little pointing would be required.
317. When the guns are laid for the projectile to strike the object aimed at without grazing between the gun and the object, the firing is said to be direct. This mode of firing is to be preferred when the object fired at is so near that the chances of hitting it are very great, and also when the intervening surface between the gun and object is so rough or irregular that a projectile striking it would have its velocity much diminished or destroyed, and its direction injuriously affected.
Direct Firing requires a good knowledge of distance, and precision both of elevation and lateral direction, in order to strike an object which is comparatively a point. It is always to be preferred when the distance is accurately known.
318. When the guns are so laid that the projectile makes numerous grazes between the gun and the object, and continues its flight, the firing is denominated ricochet.
That properly so called is performed at level, or at most at three degrees of elevation; shot will often ricochet at much greater angles, but it is not what is meant by ricochet firing.
Ricochet Firing, upon a smooth surface within certain distances, has some important advantages over direct firing. When the guns have very little or no elevation, and are near the water, as they are in a ship's battery, the projectile strikes the water at a very small angle; its flight is not greatly retarded by the graze, and it rises but little above the surface in its course. The distant charge should always be used, but the penetration is not to be depended on beyond 1,500 yards against ships-of-war.
Ricochet firing at low elevations requires only correct lateral direction, since the projectile would rarely pass over and would probably strike a vessel if within its effective range, whether the actual distance had been correctly ascertained or not.
The deviation of projectiles is, however, generally increased by ricochet, and in proportion to the roughness of the surface of the water. Even a slight ripple will make a perceptible difference not only in direction, but in range and penetration, and the height to which the projectile will rise in its bounds.
Although these facts demand attention, yet when the estimated distance does not require an elevation of more than three degrees, projectiles from guns pointed rather too low for direct firing will probably ricochet and strike the object with effect, even when the water is considerably rough. This may be called "accidental ricochet."
When the water is not smooth, the most favorable circumstances for ricochet firing are when the flight of the shot is with the roll of the sea, and that roll is long and regular.
Ricochet will be effective against small objects up to 2,000 yards, but should not commence at less than 600 yards; at less distances it is preferable to fire direct. Ricochet is of no value from rifled guns firing elongated projectiles, as they lose all certainty of direction on the rebound.
Upon smooth water, a shot fired horizontally from the 32-pdr. of 33 cwt., with 4 1/2 lbs. powder, ricocheted and rolled about 3,000 yards; the greatest range obtained from an elevation of 5°, with the same gun and charge, was less than 1,800 yards. See Dahlgren's Report on 32-pdr. of 32 cwt., p. 90.
Shot rarely ricochet at all with elevations above 5°, and the bounds are always higher, with equal charges from the same gun, as the elevation of the gun is increased.
319. Concentration of fire may be desirable under certain circumstances; and arrangements have been sometimes made to secure it by the simultaneous discharge of a number of guns upon some part of an object whose distance is known.
The advantages of these arrangements are not very obvious, excepting in cases where the position of the enemy may be visible from one part of a ship and not from all the guns in the batteries.
The object sought to be obtained is therefore to aim from in-board at an invisible target, the distance and direction of which are indicated by the Captain. It is consequently necessary that he shall be so placed as to obtain a distinct view of the enemy, or have suitable observers to inform him of his exact position.
320. In general, this sort of fire has been of little efficacy; but by the aid of a simple implement, readily made on board ship, it is believed that good results may be obtained, and particularly at night, when firing from guns on covered decks is now absolutely ineffective.
It consists of a simple metal or wooden batten, sliding in two beckets attached to the outer or inner sides of each of the brackets of the carriage, retained in any position by a thumb-screw. This batten is graduated by experiment or calculation for either the parallel or converging fire, for such points on the bow, beam, or quarter, as may be deemed advisable.
A small knob is screwed into the inner end of each batten, and a cod-line provided, with a loop in each end, somewhat longer than the width across the transom. If, then, one of the battens be drawn out to the graduation representing the degree of train required, the line stretched taut from the two knobs and hitched, and guns trained until this line is parallel to a mark on the deck, or one of the seams of the deck-plank—if they are parallel to the keel—the guns will all make the required angle, and may be fired simultaneously or in succession, as ordered.
321. The principal object in view, therefore, is so to prepare the training by anticipation, that when the smoke rises, or on sheering the vessel, the enemy shall be visible to all the Gun Captains at the same time; giving them the choice to fire at will, or on a given signal, if simultaneous fire be desired.
It diminishes the great disadvantages of guns on covered decks, where the Gun Captains can only with difficulty ascertain the direction of the enemy; and places the whole battery more completely under the control of the Commander.
322. The principal care of the Commander must be to keep his guns always bearing on the enemy, and never pass the limits of extreme train for all his guns, unless absolutely necessary in manoeuvring.
This he must regulate, either by one of the guns in his vicinity, or, better, by the aid of a bearing-plate, a species of plane-table which gives the angular bearing of the object.
323. Concentration of fire upon a particular part of an enemy's vessel may also be obtained by a general order for the guns to be aimed to strike that part when visible, leaving the Captains of guns to determine the proper time for firing, according to circumstances at the moment. This obviates the objections due to simultaneous firing, and would generally be equally effective at distances beyond point-blank. In this, as in all other cases of firing at sea, success depends mainly upon the skill, judgment, and coolness of the Captains of the guns.