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1844.] THE CIVIL ENGINEER AND ARCHITECT’S JOURNAL 05 STEAM NAVIGATION. THE GOVERNMENT STEAM VESSEL CONTRACT. Since the publication by us of the Specification and Conditions is sued to engineers for constructing engines for four second class and two first class vessels, Government have extended the space allowed for the engine room t> feet in length for both class vessels ; this is still too little : if the beam engine is to be introduced, it ought to have been extended to at least Id feet, otherwise engineers will not be able to carry out their own ideas as to the most effective mode of con struction; they will be obliged to cramp their ideas to make the en gine suitable to the Government dictates as to space. We believe the limitation originated in a great mistake, as it is supposed by many persons that the tubular boiler, which is now being very generally in troduced, occupies less space ; this is true as to bulk, but not superfi cially,for it is requisite to construct tubular boilers with as large a fire grate and back flue as for the flue boiler, for if a given quantity of steam is to be generated, the same quantity of fuel will be required for a tubular boiler as for a well constructed flue boiler. We consider that Government was most decidedly wrong in limiting the space at all; it ought to have been left entirely to the judgment of the engineer to make their own designs, and it would then have been the duty of the Government officers, to have compared each design, and decided upon that engine which appeared to them to be the most effective for permanent service, for a few feet in length in such large vessels, as from 180 to 220 feet in length, cannot be of such consequence as the eflec tive working of the engine. W e have before alluded to the necessity of Government making a rigid enquiry as to the comparative duty, expense of working and repairs of each description of engines, whether beam or direct action of the several descriptions that have been introduced within the last 10 years ; we trust this will be no longer delayed: and there is one other enquiry that ought also to be made, that is, as to the length of the Government steamers; in our opinion the second and first class vessels are too short, they would be better if built from 10 to 20 feet longer, which would give that space which is so essentially requisite to make a comfortable engine room, the most important part of a steamer. THE SCREW AND PADDLE WHEEL TRIAL. In page 85, of last week’s Journal, we gave the particulars of the Govern ment trial of the screw propeller and the paddle wheel, with her Majesty’s steam ships the Rattler and Prometheus, the former vessel was fitted with the screw, and the latter the paddle wheel; as the experiment is one of im portance, we have taken the trouble to obtain the proportions of the Rattler. We understand that as far as the build of the vessel, the proportions of the Prometheus are nearly the same. Dimensions of H.M.S. Rattler. Feet. Inches. Length, extreme 195 0 Ditto on decks 176 6 Ditto on keel for tonnage .. 157 9£ Breadth, extreme 32 8£ Ditto moulded 31 10 Depth of hold 18 n Burthen in tons 888f£ Draught of water (mean) .. 11 3 Area of midship section at 11 ft. 3 in. .. Engines—Maudslay’s 4 cylinders, aggregate 280 power 200 horses :— Diameter of cylinders 0 40 Length of stroke .. .. 4 0 Diameter of screw 9 0 Pitch of ditto.. 11 0 Length originally 5 6 Do. as reduced on the occasion of the trial 3 0 Number of threads two. The gearing at present consists of two motions, which gives a velocity of four to one of the engine. The first motion of two to one consists of a large spur wheel and pinion, the cogs of which are divided into three parts thus— those of the larger wheel being made of hard wood, and the smaller one of | iron; this sub-division of the wheels, prevents that very disagreeable rattling which is so much complained of. The second motion consists of a large and small drum, with their surfaces divided into seven convex parts, thus— upon which seven leather straps, of five inches in width, are kept tight by a suitable pulley or drum for that purpose. The drum and straps have merely been put in to try their efficiency, and to allow the multiple to be diminished or increased as circumstances may require. It is intended, when the experi ments have been completed, to remove the drums and straps, which will be replaced by a single wheel and pinion of requisite proportions. It is estimated that from 18 to 20 it.p. is absorbed in transmitting the power of the engine through the medium of straps at so great a velocity as is required to drive the screw. Diameter of Gearing. Diameter of spur wheel Feet. 11 Inches 2 Width .. .. 2 G Pitch .. 0 5 Diameter of pinion 4 4 Ditto large drum .. 10 0 Ditto of small drum 6 9 The boilers are upon the ordinary flue principle. The boilers of the Prometheus are upon the new tubular principle, the dia meter of her two cylinders 52) in., length of stroke 4ft. Sin. LAUNCH OF THE “QUEEN” NEW FERRY STEAMER. On Saturday, 12th inst., a fine iron steam boat, the property of the Birken head Commissioners, and intended to ply between Woodside Ferry and George’s pier, was launched from the yard of Mr. John Laird, the builder, North Birkenhead—amidst a large concourse of spectators, the occasion having excited considerable local interest, the vessel being of a new and pe culiar construction, which it is fully expected will greatly expedite the trip across the Mersey, particularly from the Cheshire side. She is somewhat larger than the Nun, (the largest boat now on the station,) being 110 ft. long by 22 ft. beam ; her plates and ribs are of extra strength; and she is put together with that fidelity, firmness, and improved fastenings, for which the constructor (who has had greater experience than any other iron ship builder) has long been justly celebrated. Her deck is flush, and uninter rupted by unwieldly erections, from end to end, her paddle frame-work being carried along her whole length, dying into her extremities, and enclosed by continuous bulwarks, so that the full length and breadth, including the over hangings, is rendered available for the accommodation of passengers. She is moreover finely moulded, and will doubtless prove herself very speedy. Her peculiarity consists in her being constructed that she may be propelled with either end foremost, so that the delay of backing out, and then running a-head from the shore, especially from the Woodside slip, and which occu pies on an average from four to five minutes each trip, (or nearly half the time of crossing,) will be altogether avoided—-itself a great desideratum not only as regards passengers, but expenditure of fuel. This is accomplished by a rudder at each end, so contrived that it may be fixed firmly amidships, forming a cutwater when that end (which was before the stern) is required to become the bow. So far the plan has before been in operation, though with but partial success, from the difficulty of securing the respective rud ders to form a stem, and their liability, even on slight contact at their outer edge, to be carried away or deranged. Mr. Laird has, however, contrived a remedy for this liability to damage by an outward and standing guard of iron, forming a cutwater outside the rudder when that end is the bow, and within and just clear of which the rudder works, when it becomes the stern, in which case, from its comparative thinness, it offers little or no resistance to the speed of the vessel as a stopwater. This guard is secured, below, to the keel, and above to the stern. The rudders do not rise, as in ordinary vessels, to the top of the external part of the stern post, but occupy the space only between the line of the keel and the water or draught-mark of the vessel. When not in use it is not perceptible to the eye, forming, as it were, a secret door. It is secured, when forming part of the stern below, by dropping a strong bolt, which firmly attaches its outer edge to the guard, so that the whole becomes as one piece, forming a deep holding-on fore-foot. A steam frigate for the navy has recently been built, having two rudders, with the object here sought, on the suggestion of Lord Dundonald. How she will succeed we have not yet ascertained; but we doubt not but additional strength and safety would be secured by the adoption of Mr. Laird’s “ patent guard.” Another steamer of precisely the same size and construction, and for the same proprietary, is in a forward state in Mr. Laird's yard. The Queen will be propelled by engines of 60 h.p., with oscillating cylinders, by Messrs. George Forrester & Co. (See Journal for last November, p. 307, and Plate XIII.) The engines and boilers will occupy a space of only 21 ft., leaving a large space forward and aft for cabin accommodation.