DEVICES FOR LESSENING THE DANGERS OF THE SEA.

TO THE COR. SECRETARY OF THE BOSTON BRANCH OF THE U. S. NAVAL INSTITUTE.

I beg leave to call your attention to certain devices for lessening the dangers of the sea, which, though not new, it may be well to discuss in these times when collisions at sea and along shore follow in quick succession. I have deposited at the Naval Lyceum a rough model made by my unskilled hands of a boat and davit, such as I put upon the Meteor in 1865, and which worked satisfactorily; it will be seen that it consists of two solid stanchions bolted to the side of a ship, to which are attached two flat iron davits or "dericks," connected by a spar to which the boat is hung by tackles as usual; these davits are steadied by permanent guys leading fore and set up in line with the foot of the davits, so that there is no necessity for coming-up the guys in swinging the boat in and out.

The Boat can be secured in three positions; first, ready to lower clear of the side; secondly, stowed over the gunwale or hammock netting, and last, inboard, ready to be stowed in chocks as in a vessel with a hurricane deck, or kept suspended inboard in a vessel with an open. deck. It will be observed that the tackle falls by which the boat is hoisted and lowered, pass through a leader near the foot of the davit, so that, when made fast, there will be no movement of the boat in a vertical line by the slacking or tautening of the tackles when she is swung out or in; it will also be noticed that there are two tackles attached to a short chain passing through a fixed leader on the head of the stanchions; the object of these tackles is not to pull in the davit and boat when suspended outboard, but merely to take in the slack of the chain as the davit comes in, and, on the other hand, to ease her down to the stowing point in suspension or into chocks.

In an arrangement for a large boat these pennants may be of chain, or of supple wire rope; the davit is to be kept from going too far out or too far inboard, by a toggle or other device near the upper end of the tackle block. The intention is to swing the boat in by a pennant or tackle at the end of each davit leading across the deck; the amount of purchase necessary to accomplish this, must of course depend on the weight of the boat and the number of hands available for the work; for the boat of a small yacht, it will only be necessary to pull her in and ease her out by hand; but for a heavy boat a tackle or at least a

whip will be necessary. When the boat is to be stowed in the upright position over the gunwale, a pin passing through the stanchion and the bar davit secures her there; for a large boat chocks on the rail or gunwale to land her in will be useful if not necessary. If, as in some vessels of war, a light boat is to be hung on the same davit as a cutter, it will be necessary to elongate the bar davit, curve it outward a little, and place a light spar fore and aft, as in the case of the other boat; but, for steamers carrying passengers, and for merchant vessels, two boats hung to one davit will not be proper. This arrangement, while well adapted to war ships, is more specially devised and recommended for passenger vessels and most especially for such steamers as navigate our sounds and rivers, where in general there are few expert, well drilled seamen to manage. It is an excellent plan for the smallest yacht. In examining my rough model on so small a scale it will be necessary for you to make some allowances for my imperfect mechanism. The common crooked davit is open to several objections, one of which is often mitigated by causing the davit to swing in and out through a projecting clamp with pins and holes to confine the davit in the position to lower the boat, and also to keep it upright near the side of the ship still the fore and aft guys and the Toppinglifts must be tended.

My opinion (perhaps worth very little for a man-o-war) is that no boat davit should depend much on any attachments by lifts to the vibrating masts; but that each davit should depend for its integrity on the fixtures to the hull of the ship instead of placing boats abreast of the rigging in order to avail ourselves of lifts leading to the masts. I prefer to place my boats where there is nothing to prevent swinging them directly in board, and if necessary lowering them into chocks. It may seem out of place to you, gentlemen, all of whom are supposed to be experts in devices for the management of boats and ships, for me to say so much on so small a thing; but in these days of collisions and maritime suicides it may not be in vain for me to go into these minute details, in the hope that some precious lives may be saved by adopting a simple boat davit. It may be a small thing to allude to the usual manner of arranging the tackles of boats; it is usual and I may say customary in the boats of merchant ships, and invariable in coasting steamers to place a ring in the stem of the boat somewhat far down out of the way and a swivel hook in the lower tackle block; now, in lowering a boat not provided with a patent detaching apparatus which no stranger knows how to operate, when she strikes the water down falls the heavy block, and so jambs the hook and ring that it is not

very easy to unhook it, especially if as usual the boat is bobbing up and down, and instances are not rare of jammed fingers, and of the bow being first unhooked, when the painter not being led along forward, round swings the boat and she swamps or is so entangled that she must be cut adrift. In my arrangement, as illustrated in the model before you, the ring is placed in the block, and the hook is a permanent fixture in the boat. Every seaman can easily appreciate the simplicity and usefulness of this plan as a life-saving and finger-saving device as compared to the other. I trust you will pardon me for saying so much on so small a matter. I beg leave to present to you a small pamphlet just printed and for sale by Messrs. A. Williams & Co. entitled "The life-boat and other life saving inventions." It is mainly copied from the "Journal of the National life-boat Institution for Aug. 2, 1880" by permission of the authorities thereof and contains very little original matter. My intention was to circulate freely a large number of this brochure on the occasion of the celebration of the 250th anniversary of the settlement of Boston, on the 17 instant, but, owing to circumstances beyond my control, it could not be done, and so I conclude to make the most of them by distributing them among personal friends and selling to those who choose to pay a small sum. Regretting that my health prevents my reading this paper myself, I am, very respectfully, your servant,

R. B. FORBES.

Sept. 30, 1880.

BREAKING UP OLD GUNS BY DYNAMITE.

Two old guns, captured from the Turks, were destroyed, in Dec. 1879 by Capt. Elsner, in the following manner. The guns, one 9.5 cm calibre, 1.52 m. long, the other 10 cm. calibre, 65 cm. long, with flaring mouth 17 cm. in diameter were fastened upright by burying their cascables in the earth; the vents were then plugged and the bores filled with water. The first gun was charged with 0.96 kg. of dynamite, held in two cylindrical zinc boxes, 15 cm. long and 5 cm. in diameter, which were lashed butt to butt with projecting strips of wood lashed to the sides. By this means the charge of dynamite was brought in line with the trunnions, 23 cm. above the breech. An ordinary priming cartridge.

with a Bickford fuze was attached to the upper charge and ignited. After the explosion, the cascable remained in the ground while the end of the chase, 30 cm. long, with a strip 6 cm. broad, blown from its side was found about twenty paces off, the remaining pieces, averaging from 15-20 cm. in length and from 6-10 cm. in width being scattered about within a radius of one hundred paces.

The second gun was charged with 0.72 kg. divided into one charge of 0.48 kg. with two of 0.12 kg. tied beside it. It was fired in the same manner as the first but the bottom of the bore was filled with stones to bring the dynamite in line with the trunnions. In this experiment, the cascable was split, and fragments of the gun, averaging from 10-15 cm. in length and from 6-10 cm. in width were scattered about within a radius of one hundred and fifty paces.

In examining the charges of dynamite hitherto employed for breaking up cast-iron guns, no agreement as to the necessary quantity can be found. Part 1, for 1875, of this Journal records the results of some experiments made in France, shortly before. The guns broken up with dynamite (No. 1) were one each of the following calibres, 16.4 cm. (30 pdr.), 15.3 cm. (24 pdr.), 13.4 cm. (16 pdr.), and a 32 cm. mortar. The charge of dynamite was divided into three parts, one being placed in the base of bore, one in the axis of the trunnions, and one in the muzzle; all three filling the bore completely, the spaces between being filled with water. The estimation of the distributed charge necessary was

arrived at by the following formula:

in which r is the diameter of the bore in mm., R is the distance from the axis of the bore to the outside of gun in mm., and 1 the amount of dynamite necessary, in grammes.

During the same year, two cast-iron guns of 12 cm. and 13 cm. calibre, were broken up by dynamite (No. 1), in Ingolstadt. One charge only was used-placed probably in the bore, opposite the thickest part of the gun, the remaining space being filled with water. Before explosion the gun was lowered into a pit, where it lay at an inclination of 45° to the horizon, against the side of the pit. The estimation of the amount necessary to destroy the gun by means of a single charge was obtained from the following formula:

where Q is the weight of the gun in kilogrammes. This gives one gramme of dynamite for ten kilogrammes of iron. The charge taken for the 12 cm. gun weighing 1650 kg. was 0.165 kg., and for the 13cm. gun, weighing 2360 kg. was 0.236 kg., and by them the guns were blown into twelve or fourteen pieces.

Let us compare the results obtained with the German 13 cm. gun with those given by the French 13.4 cm. gun, weighing 2220 kg. According to formula (1), there was needed for the French gun 1.47 kg. in the base of bore, 0.747 kg. in the axis of the trunnions, and 0.658 kg. in the muzzle; a total charge of 2.447 kg., ten times the amount placed in the German gun. The latter was blown into twelve or fourteen pieces and the former into one hundred and thirty pieces, the largest weighing 158 kg.

2

The heavier Turkish gun, weighing between 450 and 500 kg. was broken into about fifty pieces; the lighter, weighing between 370 and 400 kg. into about forty pieces. Applying formula (1), we have for the heavier gun r≈47.5 mm., R1 for base of bore=200 mm., R2 for the trunnion axis=140 mm., and R for muzzle=130 mm. These values substituted give 1=1295. grm., 1,=594. grm., 1,=502. grm., a total charge of 1=2.3911 kg, more than two and a half times greater than the charge used. But by formula (2) we find the charge required for this gun, L=50 grm. to be only one nineteenth of the amount actually used. For the lighter gun we have R1=200 mm., R2=160 mm., R=110 mm., and r≈50 mm.; and by substitution in formula (1) we have 1-1161 grm., 12=715 grm., 1=297 grm., a total charge of 2.173 kg. But from formula (2), we have L-40 grm., and we again find a large discrepancy in the size of the charge required. From formula (2) there can be found the minimum charge of dynamite which will break a gun into large fragments. In formula (1), it is obvious that the ratio of the charge increases as the calibre decreases.

In Part 17, "des Technischen Unterrichtes fur die K. K. Genie Truppe, we are directed in estimating the explosive charge for cast iron guns to reckon 0.1 kg. of dynamite for each centimetre of the calibre of the bore. From this we would have for the larger Turkish gun of 9.5 cm. calibre, 0.95 kg. of dynamite which was the amount used in the experiment.

Translated from the Mittheilungen über Gegenstände des Artillerie und Genie-Wessens. 1880, 5th Part by Prof. C. E. Munroe.