the pontoons, and as the pontoons sink these lines will draw the ends of the cables up through the channel-ways, where they will be clamped on top of them. Also, in sinking the pontoons, these lines will be the means of placing them directly alongside the vessel in the desired position: the cables may be evenly tightened by preliminarily raising the pontoons with a small quantity of air, and then allowing it to escape, &c., by which means the cables will be made to have an equal strain. The channel-ways in the pontoons are simply flexible hose that can be arranged to take a chain from any desired angle, as various wrecks may sometimes require; the pontoons may be moved from place to place with facility over any sea or distance on a draught of water not over 2 feet, as they are carried on a couple of longitudinal cylinders, one on each side, and so arranged that in sinking the pontoons will drop from between them, always in upright position, and at any speed the operator may desire. These cylinders also facilitate getting the pontoons in position about a wreck, when they may be detached and moved away. As any part of the full weight of a pontoon may be reduced by reserving in it a certain amount of air, one operator can readily manipulate the sinking of one of 400 to 600 tons capacity. A pontoon capable of lifting, say 300 tons, will only weigh complete 15 tons. The approximate cost will range from 19s. to 27s. per ton displacement, according to the size, the larger being the least costly.

Considering that their durability is equal to years of service, their cost is a mere bagatelle, especially as they are applicable to nearly every vessel stranded or sunken (within reach) on any coast.

Though the manner of working them on stranded vessels is somewhat similar to sunken vessels, there are some special points of advantage they possess on stranded work, beyond the mere act of lifting, that must not be overlooked.

When a vessel becomes stranded on a sandy beach the peculiar action of the sea either banks her up with sand or cuts the sand out from under her, the first of which makes it exceedingly difficult and frequently impossible to move her off by the ordinary well-known means of warping alone; and it is a common resort to attempt to dig a channel to move her through into deep water; but this is but rarely successful, because the run of the sea will fill up the channel almost as soon as formed; though in very sheltered spots it is partially successful, but an extremely expensive and slow method. Such digging is done by steam dredger or manual labour. The action of the sea in cutting under a vessel is the great cause of a stranded vessel "breaking "up" or going to pieces. Such cutting-under action of the sea may be compared to taking out part of the foundation of a house, and by thus leaving it but partially supported, cause it to tumble down. Sometimes the sea will cut under amidships,

but more generally under her ends, causing a vessel to double up and then to break away. I may confidently say that during my intercourse with wreckers in different parts of the world I have never heard of any attempt being made to prevent this cutting under, nor have I ever seen any record of its having been attempted; most probably because no practical means has yet been proposed to meet the difficulty. Sometimes a sand-stranded vessel will lie perfectly easy on the beach many weeks; when a storm or gale sets the sea running, she cuts under and quickly breaks up. It is evident the only way to protect a vessel in such a position is by a breakwater or bulkhead so placed about her as to impede the current or turn it aside; one or more of these open-bottom pontoons is the only practical and effectual means of accomplishing this purpose, as when the tide gives evidence of probably cutting under, a pontoon may be sucked into the sand, leaving several feet protruding above it, and be thus made to act as a breakwater. As regards the power of such pontoons for holding on in a sea-way or current, so little as a half-pound vacuum will give them a grip of many tons force, according to the area of their top; but when their sides are once fairly embedded in the sand, they become immovable, independent of vacuum. As it may not seem clear how a vacuum is to be got in a pontoon totally submerged, it is well to state that if the water in the hose above the pontoon, and working it, has 1 foot less height of water in it than the altitude of the water outside it, and over the pontoon, the effect of a 1-foot vacuum is accomplished.

As the quickest way of getting a stranded vessel off is to lift or lighten her, the pontoons are arranged on each side for this purpose, in which position they also act as a breakwater. As their lifting power is equal to the displacement of the water they affect, the draught of a stranded vessel may be readily reduced one-half, three-quarters, or more, which fact will invariably ensure quick flotation. Another important fact in connection with these pontoons is, that when a vessel is inclined to sand up, they may be made to entirely obviate it, by continually keeping the pumps throwing air into them, which escapes under their lower edges into the sand, and keeps it stirred up, so that the wash of the sea carries it off-which act may even be made to produce a hollow sufficient for the vessel to float in, and so gradually work her seaward. This action may also be assisted by the tubes used for chaining being passed under her, as before described; but in case a vessel is very badly stranded, and it is preferred to wait for a high tide to roll in, in order to float her, the pontoons may be arranged and securely embedded about her, ready to be inflated as soon as the proper height of tide rolls in; for such purpose they are perfectly safe, and able to stand any sea unaffected.

In working the pontoons it is desirable, though not necessary, that a quantity of highly-compressed air be stored up in a reservoir, to be turned into them when

wanted; and as thirty times the quantity of compressed air will pass through the same size tube than water (time and pressure being equal), prompt action is insured, with no risk of snapping the chains by sudden jerks, the air acting on them as an expansion cushion, and when once taut they will remain so.

On reef work a vessel may be lifted or lightened to the extent of 600 to 1,200 tons in a couple of hours after the pontoons are run alongside, attached and inflated. Of course not much can be done in bad weather on reef work, but it must be remembered that bad weather represents but a small portion of time, and reef work is susceptible of being quickly done, when all is at hand. The pontoons have no bottoms to be knocked in or injured by reefs or rocks, and are not subject to the undulations of the wave line as surface buoyancy.

The greatest strain to which these pontoons are subjected being tensile, and that of limited amount, the amount of bracing requisite is small.

DISCUSSION.

The CHAIRMAN (Sir F. W. E. Nicolson): As our time is getting short, I will propose that the usual vote of thanks be given to the author of the Paper. I almost felt tempted to say a few words about raising vessels; but as the vessels that have been raised, that I know something of, have only been in the Thames, and as the author at once acknowledges that the old-fashioned and rough-and-ready way is, perhaps, the best for smooth water, I need not say anything about it. I think he takes a very sanguine view of the probability of raising vessels in rough and deep water. He does not say his suggestions have ever been tried. Of course any person who can devise a means of raising vessels in deep water and in a rough sea will confer a great boon upon the world at large. I am very sorry to say that collisions between steamers seem to increase, and they have a great knack of going to the bottom at once, which the good old-fashioned wooden ships would not do.

Mr. HENRY LIGGINS: Will you allow me just to draw attention to a fact which will be in the recollection of many gentlemen here. Really, the matter comes so suddenly before me that I have forgotten the name of the ship to which I am alluding-I think it was the London; but it occurred a few years ago at Tayport, at the entrance to the river that runs up to Dundee. Admiral Sir Henry Keppel and Mr. Page, the engineer of Westminster Bridge, devised a scheme for pumping air into that vessel; but, after many weeks of work on her, they found it utterly impossible to make her air-tight, though she was partly out of the water at low water. There were so many cocks, scuttles, and hatchways, that, although they succeeded in stopping those parts that were easy to reach, they found it utterly impossible to make her air-tight; and therefore they could not pump their compressed air into her.

แ

After trying for many weeks, and spending a large sum of money, the affair was abandoned; when an old-fashioned shipwright—an old-fashioned man, from a yard in Dundee—thought of an old-fashioned plan of raising her, which if adopted he thought would possibly get her up. He was supplied with some money, and allowed to make the attempt, and in less than a week the vessel was afloat and in the dry dock at Dundee.

Admiral J. H. SELWYN: There is a statement in the Paper (see p. 197) which I do not think anybody here understands, with regard to vessels:-"As it may not seem clear how a vacuum is to be got in a pontoon totally submerged, it is well to state that if the water in the hose above the pontoon, and "working it, has 1 foot less height of water in it than the altitude of the water outside it, and over the 66 pontoon, the effect of a 1-foot vacuum is accomplished." I confess I am utterly unable to see how that is proposed to be done. It is given as an explanation, and I think if the author could be induced to explain it, it would be desirable.

The CHAIRMAN: Unfortunately the author is not here, and it is not part of my duty, happily, to explain the author's meaning.

[With regard to this the following explanation has been received from the author:—

The statement which Admiral J. H. Selwyn refers to, is really somewhat ambiguous as it reads, but that paragraph suggested itself to me by the fact, that objections had frequently been made that water could not be raised over 32 feet by suction: this is so when raising it above the surface of water, but it may be raised from any depth below the surface by reason of the surrounding pressure; without the aid of this surrounding pressure water could not be raised by suction at all in any position or condition. The word "vacuum," in the paragraph referred to, is unfortunately used in a general sense (in order to avoid verbosity) and not in a scientific sense, as it is clearly impossible to get a vacuum in an open-bottom pontoon; but its internal pressure may be reduced more or less below its external pressure when its open bottom is sealed, or partially sealed, in the sand; and the result is that the pontoon is forced deeper into the sand, as the tendency of nature is to equalize pressures, and consequently the pontoon sinks into the sand as the handiest means nature has of avoiding a vacuum, or meeting any tendency thereto: but a vacuum itself is never got, and if it could be got would undoubtedly nullify the value of the pontoons, as when they are sucked into the sand they are necessarily filled with it to their tops, thereby anchoring them immovably. In answer to the Chairman's remarks about the apparatus being tried, I would say that the chaining part has been handily and satisfactorily done on vessels buried several feet in the sand, and in up to 30 feet of water. A pontoon having a capacity of 10 tons has been most satisfactorily operated on in the sand to show its facility for sinking, &c., but no regular organization has yet been formed for working the entire apparatus, owing partially to the circumstance that the inventor has been profitably engaged in another business which he cannot well neglect, together with the fact that through the universal commercial depression that has been ruling for the past two years it is difficult to get up an organization to work the apparatus properly; besides which all radical changes in an art seem to require a long consideration on the part of the public before being acceptable to their patronage. The publicity given to the system and apparatus by your Institution is certainly most valuable in revealing its merits and demerits, and it must now depend on its intrinsic worth alone and not on any further efforts of mine for its introduction.]

ON THE TELEGRAPH CABLE SHIP "FARADAY."*

By C. W. MERRIFIELD, Esq., F.R.S., Associate Member of Council.

[Read at the Seventeenth Session of the Institution of Naval Architects, 7th April, 1876; Vice-Admiral Sir F. W. E. NICOLSON, Bart., C.B., Vice-President, in the Chair.]

It occurred to me that some account of this vessel and of her performance ought to be given to the Institution, and I have therefore, through the kindness of Messrs. Siemens, obtained such particulars as I thought would be of most interest. Her builders were Messrs. Mitchell and Co., of Newcastle-on-Tyne. These gentlemen designed her, so far as regards all details of naval architecture and construction. The special fittings relating to telegraph work were arranged by Messrs. Siemens, and the bilge keels are due to Mr. Froude. You will see by the model and drawings before you what her general construction is—a double-ended ship with a rudder at each end, 360 feet long, 52 feet beam, and 36 feet deep, drawing usually at load draught from 22 feet to 24 feet. She has a flat floor, rather square bilges, with large external bilge keels, and is usually sailed on very nearly even keel. The vessel has three cable tanks, having an aggregate capacity of 109,500 cubic feet exclusive of the central cones. The form and displacement is such that the vessel will carry 4,300 tons of cable and water in tanks, 150 tons of stores and cable machinery, and 1,400 tons of fuel, or a total of 5,850 tons dead weight, all told, at about 26 feet mean draught of water.

GENERAL DESCRIPTION.

The hull of the vessel is built in accordance with Lloyd's Rules to the highest classification, namely, 100 A1. In addition to Lloyd's ordinary requirements, the vessel is further strengthened by having the upper and middle decks of iron from stem to stern, and the lower or orlop decks also of iron from the boiler room to foremast; the upper deck is also covered with pine planks; the main deck in the parts occupied by cabins is covered with wood. The construction of the tanks, iron decks, hull, inner

* Received 7th April, 1876.