will enable it to be completely ventilated, unlike the ordinary cabin between decks, which is so unpleasant that ladies and delicate persons endure the worst weather on deck rather than accept shelter in it.

"But one of the greatest advantages of this saloon is that, whatever motion the ship may take from the waves-and this, from the adaptation of her form to passivity among channel waves, will be slight the saloon will be practically free from it. It is in the middle of the ship, as regards length and breadth; and the axis of rotation is at a height where there is least motion; so that, as regards its position, it is one in which the vertical and lateral motions, produced in every part of the ship by the pitching and rolling, will be so small as to be inappreciable. The cabin will also have no sensible pitching motion, for the form of the vessel is such as to make it impossible for the sea of the Strait of Dover to raise the ends very considerably; and even the small effect produced at the ends of the ship will be reduced by one-seventh at the extremities of the cabin. The rolling motion of the ship on the intended service cannot be very great, from the resistance of her paddle-wheels, her size, form, and speed; but, such as it is, it will not be communicated to the cabin, for the perfect action of Mr. Bessemer's hydraulic apparatus is an established certainty, and not a matter of speculation, and it will always insure the floor being kept level.

"The governing principle of this suspended saloon consists of a set of powerful hydraulic apparatus connected with the underside of the flooring, and so arranged that, as the vessel rolls to either side, the pressure or resistance afforded by the water is instantly brought into play and utilised in checking the motion.

"The floor, beneath the saloon, is composed of riveted iron beams, with smaller rafters attached to them. This floor, at its ends and at two intermediate points of its length, rests on steel axles, of about the diameter of the driving axle of a locomotive. The supporting frames are securely fixed to the double bottom of the vessel.

"This floor is capable of a motion like the beam of a pumping-engine; and if as much dead weight be placed below the beams of the floor as will counterbalance the upper part of the structure, the saloon will be in a state of equilibrium and capable of motion on its axis. In this condition it is liable to be put in motion by the movement of passengers or by the force of the wind blowing against the upper part. But the hydraulic power here applied prevents any such erratic motion, and affords means of retaining the saloon in a vertical position at the will

of the man operating the apparatus, notwithstanding that the vessel in which it rests is moving beneath it.

"In order to effect this end, a toothed sector of large diameter is secured to the main central axis of the structure, and beneath it is a strong bed-plate firmly attached to the floor of the ship. On this bed-plate are two hydraulic cylinders, to which a double-ended ram is fitted, the central part of the ram being provided with teeth, which gear into the sector. Therefore when the ship is in a state of rest, the sliding in and out of the rams will cause the saloon to move on its own axis with a gentle but powerful motion. These movements, however, are controlled by a pair of delicately-balanced equilibrium valves.

"Hence it will be seen, that when the ship is rolling at sea, this power of acting on the saloon enables the steersman to retain the saloon constantly in a perfectly vertical position, while the floor of the ship is rising and falling beneath it. The essential point of this arrangement is that the hydraulic apparatus has not to put the saloon in motion, but simply to prevent it acquiring any motion. Moreover, the vis inertice of a structure like the saloon, which will weigh some seventy or eighty tons, will greatly assist in resisting the initial tendency to motion.

"In other respects Mr. Bessemer's saloon offers undoubted advantages. Resting, as it will, on four axial supports bedded on an elastic packing of large area, it will be completely insulated, and will not be susceptible of the violent tremulous motion imparted by the engines and paddles. Again, the heavy shocks of the sea against the sides of the ship, so objectionable in cabins built against the framing of the vessel, will be wholly unfelt, as there will be a space of five feet between the saloon and the sides of the ship, from which, in fact, it will be totally disconnected."

Fig. 1 of Plate XCII. is a section of the ship taken right through the saloon. The strong black line shows the moving part.

It will be observed that the attempt to neutralise the motion of the vessel by that of the saloon addresses itself to the rolling only. It does not affect either the translatory part of a ship's oscillation, or the pitching. I agree with the promoters in thinking that, in such large vessels as they propose to use, and with the saloon in the middle of the ship, the pitching will be small in amount, and slow; and that, taken alone, it will not be sufficient to cause sea-sickness. There is, however, another kind of motion affecting the ship, which requires fuller consideration.

In the regular heaving of the sea, after the wind has blown sufficiently long to cause regular waves or swell, each particle

of water describes a circle in a vertical plane. At the surface, the diameter of these circles is the whole height of the wave, from valley to crest. The circles rapidly diminish in size as their depth below the surface increases. Taking into account this diminution, as well as the effect of the ship's breadth, it is certain that the ship will not follow this circular motion at all to the same extent as a cork floating on the surface. In moderately heavy weather, it is probable that, in such a ship as that which Mr. Reed has designed for Mr. Bessemer, any fixed point would describe a vertical circle of five or six feet in diameter in rough weather, quite independently of any rotatory or rocking motion. The model exhibited at Denmark Hill simply oscillated on a fixed centre, and therefore the experiment did not go to this point, as it might have done if it had been mounted on a crank or eccentric. It does not, therefore, tell us how far this remains as a real cause of uneasiness, especially when combined with a small amount of pitching, after the rocking or rolling is got rid of. While, therefore, I am unable to look forward to the absolute prevention of seasickness with the full confidence expressed by the promoters, I have not the slightest doubt that the remedy will be all but absolute, and that the residual motion will only affect extremely sensitive persons in exceptionally rough weather. Even for these, it will be nothing like what they undergo at present. The invention of springs has not entirely cured the shaking of a carriage; but I believe that the comparison of the motion in the Bessemer saloon with that in the present boats, in a rough sea, will be much the same in degree as that between a well hung carriage and a waggon or tumbril on a rough road.

The mode of propulsion, by two pairs of paddles, one working in the wash of the other, is not very favourable to economy of fuel. There is practically, however, no help for it; and as the voyage is a short one, this question is of secondary consequence. The great length and breadth of these vessels will make it somewhat more difficult for them to enter the French harbours than for smaller boats; and therefore there will, I think, be a few rough days in the year when smaller vessels will have to perform the mail service. With this reservation, I have no doubt as to their being perfectly safe-in fact, all the safer on account of their large size. An accident to the saloon, or to the machinery which moves it, would simply have the effect of setting it fast, and the worst that could happen from this cause would be, that the passengers would not get the relief desired, but would simply be as in the saloon of an ordinary ship, only with much better ventilation.

Another plan, remarkable for its divergence from the ordinary form of ships, is the double steam-ship proposed by Captain

Dicey. A sketch* of this type of ship is given (in section) in Fig. 2.

Imagine that an ordinary ship, 45 feet broad, and 350 feet long, is sawn right down the middle, longitudinally; that the two halves are separated by an interval of 30 feet; that a flat side is then fitted on the inner side of each half ship, and that they are then bridged together by a strong platform, which connects them rigidly. There is thus a clear waterway, or rectangular canal, 30 feet wide, along the whole length of the ship, right down the middle, open at both ends and at the bottom, but covered at the top by the lower deck of the saloons. Propulsion is effected by a pair of ordinary paddle-wheels placed in this canal, right amidships--one paddle being close to each flat side, with a clear waterway ten or twelve feet wide between them.

I can quite bear out the promoters' claim for this design in respect of easy and gentle motion in a rough sea. it is now more than twenty years since I first assisted at experiments with models of twin boats, and I have recently had the advantage of sailing in a schooner yacht of this build. I know that these ships are remarkably steady, and so far as concerns the mere question of immunity from sea-sickness, I think that they are only second to Mr. Bessemer's plan. If sea-sickness were the only difficulty of the channel passage, I should desire nothing better than Captain Dicey's ship to go across in.

The objections are, that these vessels are unhandy, and steer badly, and that their form is ill adapted for speed. These are very serious faults, and render them unsafe vessels for the channel service. Our mail steamers frequently find it no easy matter to enter Calais harbour, or to cross Boulogne bar in safety, and they sometimes have to give up the attempt. Now every one who has experience of twin boats with flat sides, is aware that they cannot be depended on for steering in a heavy sea. Their flat sides make them answer the helm very sluggishly, and at the same time give double effect to the tendency of the waves to turn them against their helm. This is a bad quality in the open sea; it might be a fatal quality in attempting to enter or leave a gutway in a cross sea-like Boulogne harbour in a south-wester. The danger is enhanced by defective propulsion. A twin ship has nearly twice as much wetted surface as an ordinary vessel of the same displacement. As a large part of

* This sketch must not be considered authentic, except as regards its general shape, nor as being correct in its dimensions. The writer has not had access to accurate plans, but has only seen a model; and as he was unable to speak favourably of the project, he did not think it right to apply to the promoters for information about details. The sketch is quite sufficient as an illustration to this paper.

the resistance of a ship is due to friction, this is one obstacle. In the next place, every vessel carries before it a wave of displacement and a frictional wave. These diverge from each bow, whether one side of the bow be flat or not. A flat bow certainly diminishes the wave of displacement, but it does not annihilate it, and it scarcely diminishes the frictional wave at all. From these two causes there is a heaping of the waves in the channel, which forms a great source of extra resistance. In sailing vessels of this form the extra resistance is compensated for by the extra sail-carrying power of this type, but there is no such compensation in a steam-vessel. Then, again, the mode of propulsion is so bad—I should have said the worst possible, were it not that one of the directors of the Dicey Company has proposed to substitute a water-jet propeller for the paddles. There can scarcely be a worse position for a paddle-wheel than half-way along a rectangular channel. The propulsion is affected by the reaction of the water, whose backward velocity relatively to the ship is greater after it leaves the paddle-float than before it meets it; otherwise there would be no propulsion. Now the sectional area of a stream of water is inversely proportional to the velocity-for the quantity of water that passes any section of it is constant-and if the section is uniform, there must be a difference of level, or eddy-disturbance, or waves, either of which take up part of the work which ought to be expended upon propulsion. This occurs to some extent with outside paddles; but it is very much enhanced when the paddle is placed in a confined channel-not to mention the increased frictional resistance of the paddle race. I believe I am within the mark in predicting that, for the same speed, Captain Dicey's boat will require twice the engine power of that designed by Mr. Reed and Mr. Bessemer. It is not probable to my mind, that with such a ship, and such a propeller, a speed of twenty or twenty-one miles could be reached at all, no matter what the engine power might be.

Besides the danger from want of steering power, there is great danger of the paddle being carried away or disabled by a great wave, the effect of which would be guarded from dissipating itself laterally by the sides and roof of the canal in which the paddle works.

As regards the connection of the two hulls by means of the platform, I do not think that this presents any mechanical or practical difficulty, except that it will require a great weight of iron, and that this will have to be met by increased draught of water. This is itself an evil where tidal ports have to be entered; and it also takes up engine power.

In short, I have come to the belief that Captain Dicey's twin ship will be easy, but that it will not be fast, economical, or safe.