THE POLYPHEMUS.

Lyttelton Times, Volume LII, Issue 5807, 6 October 1879, Page 5

THE POLYPHEMUS.

(From the Times, July 20.) ;The torpedo ram Polyphemus, now being constructed in Chatham Dockyard, appears likely to be the most extraordinary ship that has yet been built. She is novel and peculiar alike in form, structure, fittings, and arrangement of armour protection• while her weapons of attack are such as will necessitate her being fought differently from any other war ship. Her design was described by the late Mr Ward Hunt in the House of Commons on March 12, 1877, as being “ of a kind as yet unknown in any part of the world, but which has been much tajked about, and has been at last forced upon me by that gallant officer who stands at the head of the veteran list of the Navy—viz., Sir George SartoriuS, who has shown that although his age is great, his mind is still youthful, and that he is willing to receive new ideas and able to inculcate them.” The leading features of the Polyphemus are a strong ram bow, a powerful torpedo battery, great speed and handiness, moderate size, and a Small extent of surface above • water exposed to the enemy’s fire, such portion of the vessel as is above the water-line being convex in form, so as to deflect any projectile that may strike it. The appearance she will present when at sea will be that of a cylinder, floating on its side and deeply immersed, which is tapered at the ends to 'form a bow and stern. The top of the cylinder will be 4ft 6in above the wa’er-line, and will be flattened over a large portion of its area to form a deck. The whole of this flattened cylindrical surface will bo plated over with steel armour, and will cover in and protect the ship and all her machinery'and fighting appliances. The ship proper as she will thus appear will be surmounted by a light structure carrying a hurricane deck of about twothirds her length, and upon this deck will be seen a signal-mast, funnel, pilot tower, boats, and other fittings; Underwater the form of the Polyphemus is as 1 strange' as at will thus appear above. The cylindrical curvature of the sides is carried down several feet below the waterline, and armour-plated to that depth. Below this point the section assumes a V form, and ends in a sharp angle at the keel. It will therefore be seen that a complete cross section of the vessel is very similar to that of a pegtop. The flattened convex curvature i of' the upper part of the peg-top would represent the part'of the Polyphemus'that is above watdr; and the lower portion, which ends in a point, would alio represent the part of the ship that is below water. If the peg-top be imagined to float in water at a depth below wherw its breadth is greatest and where the section thus.' begins' to : curve towards the centre line, a- rough idea may bo obtained both of the form and proportions of the above and under water parts of the Polyphemus. The Polyphemus is 240 ft long between the perpendiculars, 40ft in extreme breadth, and will hare a load draught of 20ft. Her displacement will be 2640 ton*. The convex armoured deck will be 4ft 6in : above the .water-line, and will be completely plated over with steel armour Sin thick. .This armour will be carried to a depth of 6ft to 7ft . below the water-line. The Polyphemus will not be fitted with masts or sails, but will carry a pole for signalling purposes and foe making observations from.. She will be propelled by twin screws, and will have two'pairs of highprsssure compound horizontal engines, which j are being * constructed by Messrs Humphreys and'. Tennant,' of’ Deptford. Each., high, pressor* cylinder’ will be 88in ha diameter, and the law [pressure 64in. The stroke will I># *6in. Ib# botlsn will be of feelNoiutta

typbi 12 in number, and will he made of steel. Ihey will work up to a pressure of 1101 b per square mob,, It is estimated that the enginee Jill indicate a collective power- of 5500 17 »P eed of the ship .will be _.? bo on ty offensive weapons the Polyphemus a Powerful ram bow and Whitehead torpedoes. She will have no gun#at all, except a few light shell gun# and Gatlings on the hurricane deck for the pnr”t? eUln s boafc or torpedo attack. Ihe ram wifl consist of a veiy strong spur, Wft in advance of the item of the ship, and is so placed that it will vflra i o ®i' below an enemy’s armour, lb will be connected to the stem and how by deep web plates and angles on each side s theformer being a continuation of the 3m deck armour, which is curved downward# at the bow and carried under water till it reaches the level of the spur. The spur is being fitted so that it may be unshipped and taken off the iteni'when not required for active use. Under the ram is a torpedo port; which will enable Whitehead torpedoes to ! be ejected right a head of the ship. Xhfcrtarealsb two torpedo ports on. each side amidships,' from which they will be ejected on the* broadsides. The ports and apparatus for working the torpedoes will be upbn the System fitted in the Vesuvius and Qlatton. All the torpedo ports are under water,.‘but it !« understood that this under-water' attack will be -supplemented by torpedo firing above water from the ■ armoured. deck upon the systemadoptedin ordinary torpedo • munches. ; „bove the (armour-plated portion of the huU » hurricane deck is fitted for about two-thirds of its' length. Ihis deck is about one-half the 1 extreme breadth of the-ship,- ’ Communication is made between the hurricane deck and the interior of the ship by openings cut through the armoured deck/ 1 The openings thus cut are protected by glacis plates and armour, and by casings, which art carried up to the hurricane deck. The boats are carried upon the hurricane deck,' and the ship is steered and worked from it.i < Am-'armoured‘pilot tower,- with protected mean# Of access to the lower part of the ship, is placed at the fore end Of the hurricahe deck; and fitted with steering wheel, telegraphs,'voice pipes, apparatus for firing off the torpedoes, and all other appliances for conning and working the ship. A few light shell or Gatling guns will' also be carried on the hurricane deck, as we'have stated,-for repelling boarders or torpedo- , boats. -

The Polyphemus is built throughout of steel. The frames are of Bessemer, and the bottom plating of Landore-Siemens steel. She is - constructed upon the usual system of transverse -bracket frames and contibuous longitudinals, and has a double bottom the whole length of the ship right up to the upper deck. ■ a -:- ■' The subdivision of the lower part of the ship into-small watertight compartments has been carried as far as appears possible. ‘ The double bottom is split up into a large number of cellular spaces, and the hold is divided by a- longitudinal middle line bulkhead; and numerous transverse bulkheads. The boilers are contained in four separate watertight compartments of the hold, three being placed in each; and eash pair of engines is also contained in a separate watertight compartment. The advantage of such an arrangement is sufficiently obvious in view of the possibility of one of the boilers or enginerooms being bilged by a blow from a ram or torpedo. The double bottom is arranged so as to include the coal bunkers, as in the Devastation and the Inflexible. By these means buoyancy is gained if one, of the compartments is opened up to the sea, as the water can only find its way among the interstices of the coal, and a large quantity is thus kept out of the ship. The cabin and accommodation for the crew will all be below the armoured deck, and will be ventilated Wt-ilJcially, ttsin the 'ironclad monitors. They will be lighted throughout by the electric'light, which is being fitted in several ironclads, and is likely to becoma extensively used for this purpose. An electric light will also be fixed in the look-out oh the polemast, for reconnoitring and signalling purposes. The most remarkable and novel feature in the ship yet remains to be described. The bottom plating on each side, instead of ending in a keel, or flat keel plate, at the middle line, is formed into a recess; so that in -place of a keel there is a rectangular groove, Ift Sin wide and 3ft deep, taken out of the .bottom of the ship. This grove or recess.is intended to be filled with cast-iron ballast up to a weight of 300 tons. The ballast will be east in several lengths, and will be so attached to' the ship that, in the event of a compartment becoming bilged, and its being} desirable to lighten the ship, the ballast can be let go and dropped from any part, as may be required. The draught and trim may thus be regulated to a certain limited extent should the vessel be damaged inaction. This is-a point that will probably be discussed among engineers. The object of carrying the ballast seems to be to keep the ship down in the water, and prevent the deck from becoming too much exposed when the ship is uninjured; but should she become still further immersed from any cause; the dropping of the ballast will somewhat relieve and lighten, her. The utmost effect of the ballast will be to enable the vessel to float 12in to 14in lighter when it is dropped than she would do; before. In other words, although her armoured deck is only 4ft Cin above the water, and this height only is exposed to the enemy’s fire, - the surplus buoyancy, on account of the ballast, will be the same aa though the armoured deck stood sft 6in or sft Sin above the water line.

It ■will be obvious that this quantity of ballast, amounting to about one-ninth of the whole weight e£ the ship, cannot be carried about for nothing. It adds to the work the engines have to do, and a greater expenditure of engine power for a given speed will be required to enable the ship to drag the ballast about with her. The additional engine power that will be required to d rive the Polyphemus at full speed, after adding the ballast, will necessitate an increased coal consumption of nine to ten per cent., and a corresponding reduction in coal endurance. It will hardly be considered necessary to carry about all this dead weight in time of peace; and it will be a question for practical consideration whether the carrying of it about in time of war at acoet of reduction in speed, or in coal endurance—and this in a ship whose coal supply is very email for her power—will be compensated for by the armoured deck being 4ft 6in out of water, instead of sft 6in.

The Polyphemus is more or less of, an experimental character, and the building of future ships, possessing some or all of . her .characteristics, will depend upon the result* of her trials. She is not likely to creates great revolution in war ship-building, or to show that guns are unnecessary in a fleet. Indeed, it must be evident; that there are many operations—such as the bombardment of fortifications, which could only be carried out by ships armed with guns. The question respecting the Polyphemus is not whether such vessels as she are to supercede, gun vessels, but whether she may not serve; the more, humble, though very useful, purpose of starting a type of war ships that will be valuable auxiliaries in action. Mr Ward Hunt, on the occasion before referred to, spbke of Her as follow*: “ This vessel must, of course, to a certain extent, be regarded as an experiment; and, even supposing it to be a success, I could nob propose it to the House,, as being likely to supercede all other kinds of fightinganips, but only as a useful adjunct to a fleet in case of war.. Probably it would not be desirable that she should be kept .at sea for a long period at,a time, but. I venture to think she will prove a very formidable weapon, and if she should be a success, she .may perhaps be r ®g* r ned_ as a sort, of rival to those monster ships with tremendous- armour that; we hear spoken of as likely to be built in some foreign ports.” b *o*o° p dyphemus w,s commenced in Sept., 1878, .and is already far advanced, being entirely. framed • and plated, except at the extreme ends.. . Great progress is being made with her,and she could be got ready; for launching mi vgry few months, t , un