above. The collision bulkhead would be better further The Marine Engineer. aft, so that it should be quite clear of all the SOM LONDON, APRIL 1, 1896. strengthening pieces supporting the ram; it should be more strongly fitted than at present, and should be rounded like a barbette, instead of being at right angles to the side. In the case of such doors as are absolutely necessary, the proposal is that they should be modified into smaller rectangular openings close to the deck at the top of the bulkhead, to which access could be had from the floor of either adjoining compartment by a short ladder. The result of the carrying out of this proposal would be that in each compartment that had doors the water would meet with five, six, or more feet of bulkhead all round, which would confine any sudden inrush of water in the one wounded compartment for an appreciable time to enable the doors to be closed upon it, and the sudden rush of water from compartment to compartment, as at present takes place when the sills of the doors are down to the floor, would be avoided. Lord Beresford is aware that this removal of doors might materially affect the ventilation of compartments as at present relied on, but he considers that point could easily be met by special mechanical arrange (OME months back we expressed an opinion that there was not at that time any approved system of watertight doors extant, which would give the necessary immunity from danger in the hurry and confusion of an unexpected accident, and which at the same time would be free from almost insuperable objections in use. We see that this opinion is practically confirmed by two papers read upon this subject before the Institution of Naval Architects. One of these is the contribution of Lord Charles Beresford, who characteristically cuts the knot of the difficulty by the suggestion that watertight doors of any kind are to be looked upon as an evil, even if unavoidable in certain cases, and that the number should be considerably reduced as compared with the modern practice in war vessels. He epigrammatically defines the watertight door to be a compromise between the safety of the ship and the convenience of the department, and considers the departments, if faced. ments ought, as far as convenience may go, to give more way to the safety, as it has so often been proved that the doors are invariably open when an unforeseen contingency occurs. The examples of the Victoria, the Re d'Italia, the Vanguard, the Grosser Kurfurst, and the Blanca Escalada are fresh in our memories, and it was reported in each case that had it been possible to close the doors in time, the ships would have been saved. Lord Beresford believes it to be a fact that no ship has been saved when wounded below water level at a moment when her watertight doors were open, and we cannot contradict him. Hence, he argues, is the danger of her having the doors at all. He tells us that the French have almost entirely done away with water-tight doors in their new ships, and he therefore ventures to advise that there should be no doors at all below water-line in the bulkheads which enclose the engine-room and boiler-room compartments, which form the belly of the ship, that is the great floating power from which she gets her buoyancy. Immediate communication between the engineer officer and his subordinates would, he thinks, be satisfied by quick, verbal communication, and after personal transit from compartment to compartment, could, he thinks, be obtained through doors above the water-line. The next most important place in which there should be no doors at all is, he thinks, in the collision bulkhead, and in the next bulkhead aft, and that the only access necessary to the foremost compartment should be by he manhole in the deck. COLONEL N. SOLIANI, Director of Construction of the Royal Italian Navy, considers that in the matter of watertight doors we may have something to learn from our neighbours, and though not going so far as Lord Charles Beresford in desiring to avoid them as much as possible, despite loss of comfort or convenience, he details many suggested improvements in form to make them more reliable and prompt in action. He distinguishes, however, between doors which should always be normally closed, and only opened for special occasions, to be immediately closed thereafter, and those doors which are constantly being used. In the former case he considers hinged doors are suitable, as making, when time is not urgent, the most reliable form of watertight joint. In the latter case he considers the doors must be sliding, and prefers the door to close by. falling vertically by its own weight, and operated by a brake screw gear for lifting. The release of the brake disengages the lifting gear to allow the door to fall, which can thus be checked in its fall. The main. difficulty, however, in sliding doors, is to make a reliable watertight joint, particularly against water pressure from either side, and Signor Soliani advocates a double door, making an automatic water joint either way by pressure from either side. The bunker doors are a still more difficult problem to ensure tight closing, as so often coal lies upon the threshold just where the lower edge of the door should make a joint. The Colonel proposes to overcome these difficulties by raising the bunker aperture some distance above the bottom of the bunker, and a foot or more above the floor of the stokehold. Coal could not thus rest on the threshold, and even if there, would be lifted and thrown down by the rising door, which might have a bevelled edge for the purpose. Although it is easy to devise automatic gearing, either electric or hydraulic, by which the doors might be immediately closed by the officers on deck in emergencies, the awful fate of a sailor or stoker caught under such closing door, and actually confined by its closure in either the coal bunker or a flooded compartment, will, we fear, stand for a long time in the way of such arrangements being adopted, or if adopted, in being promptly or efficiently worked when needed, so we are inclined to fall back upon Lord Charles Beresford's idea to ascertain how many doors through bulkheads can be dispensed with entirely. IN the estimation of the stability of ships in still water, the development and latest outcome of geometrical solutions are well set out by Mr. J. Bruhn. He traces the first conception of geometrical analysis as to the problems of stability from Bougner, who first discovered the meta-centre, and defined its properties and importance, to Euler and Dupin, the latter of whom Mr. Bruhn credits with complete exploration of the geometry of the subject. He traced the movement of the centre of buoyancy under all conditions, and defined the character of the surface traced by it. Mr. John, Dr. Elgar and Professor Jenkins followed these geometrical investigations to further development, and were followed by others. Based on the geometrical work of these investigators, Mr. Bruhn sets himself the task to work out certain propositions, the first of which is-To construct geometrically a set of cross-curves of stability for inclinations from 90 deg. to 180 deg. when we know the corresponding curves for inclinations from 0 deg. to 90 deg. The second is-"To determine the direction in which the centre of buoyancy moves when the ship is inclined in a given direction," and he follows with investigations of lines of curvature and geodetic lines as curves of buoyancy and relations between the surfaces of buoyancy and floatation. These propositions are worked out with great clearness, and with reference of course to geometrical figures and constructions, which are the essence of the investigation. THE estimation of the stability of vessels under all circumstances, and the determination of the periodicity and amplitude of the rolling of vessels in a synchronous or disperiodic swell, have given a large field for the close investigation of mathematicians, and the Institution of Naval Architects would do less than honour to its functions were it not to give to the world at large, through its members, great accessions to the knowledge in such subjects, though the matter is rather too deep for the general reader. Mr. R. E. Froude is a worthy successor to his father in further developing such mathematical investigations, and is not to be outdone by the eminent French savant, M. Bertin, in the abstruse calculations as to the non-uniform rolling of ships, that is, the rolling on a non-synchronous or disperiodic swell. We are glad to see, however, that Mr. Froude in his paper does not merely give closely analytical investigations in these matters, but, for the benefit of those who try to follow him, puts his results in plain verbal propositions, embodying in as simple a manner as possible a compre hensive view of the theorems at which he has arrived. These are, first-" In an isochronous resisted ship, rolling under the influence of any swell whatever, the difference in the rolling due to any difference in initial angle and angular speed, consists simply in the superposition of a corresponding still water, or (as it is termed), free oscillation." This leads to a second general proposition, thus-"In an isochronous unresisted ship, rolling under the influence of a swell, consisting of any kind of truly recurrent undulations, the rolling will consist of the uniform forced oscillation proper to these undulations, with or without a free oscillation superposed." On this follows the consideration of resistance upon such non-uniform rolling, which leads to the following conclusion. That the "free" oscillation becomes the resisted still water oscillation, or in other words, the familiar "extinction diagram." The differences of a resisted forced oscillation from the unresisted may also be defined as an alteration of phase which precedes or follows that of the unresisted in a definable degree, and could be dealt with under the first and second propositions. The following characteristics of results in resisted rolling are also very general-(a) however non-uniform initially, the rolling ultimately falls into the uniform forced oscillation; (3) it does so the sooner, cæteris paribus, the higher the resistance; (c) the fewer the cycles or alternations of amplitude of rolling, the more nearly synchronous the swell of the ship; (d) the amplitude of the uniform rolling is an approximate mean of the alternate maxima and minima of the precedent nonuniform rolling; (e) if the rolling starts from zero, the maximum amplitude falls short of twice the ultimate uniform amplitude; (f) and the more so the higher the resistance; (g) and the more nearly synchronous the swell; () in a synchronous swell the maximun amplitude cannot exceed the ultimate uniform amplitude unless it does so initially. In practice, however, it has been found that the ideal assumed uniformity of swell does not exist. Hence, in proportion as on the one hand the resistance is small, and initial non-uniformity of rolling dies hard, and on the other the non-synchronism is considerable, and the alternations of amplitude rapid, the continual fresh disturbances due to non-uniformity of swell avail effectively to maintain non-uniformity of rolling in spite of the tendency of resistance to eradicate it. depositing of goods, it it particularly suitable to shiploading and discharging, in connection with which work the saving of time is often a matter of the greatest worked with this gear in half the time, with the same consequence. We are informed that cargo can be number of hands-and even with fewer handsrequired under the old system. This valuable quality of time and labour saving has, indeed, already been adequately tested by working some thousands of tons of general cargo on a large liner, to whose owners reference can be given. The gear, it may be added, TYZACK'S IMPROVED CARGO GEAR. E have pleasure in presenting to our readers the above illustration showing the working of the improved gear for loading and discharging steamers and sailing ships, and for use also at wharves, warehouses, &c., which has been introduced by Mr. George Tyzack, the well-known anchor patentee and manufacturer, South Shields. Mr. Tyzack has, for years, given very close attention to this subject, and we believe that in the present gear he has perfectly realized the object he had in view, which was the removal from one position to another of packages and heavy weights generally, with the minimum expenditure of time and labour. Though the gear is adaptable to any purpose involving the lifting and re can be easily and quickly rigged into position by any seaman, and can be worked upon ordinary booms or upon outriggers. For light goods, say up to a ton or 30 cwt., single purchase may be employed to enhance speed of working, the double purchase being resorted to when heavier lifts are required. The cargo runner used may be either rope or chain. Cargo when traversing travels in a direct line from headroom over hatchway to the required distance over vessel's side, and traverse is materially assisted by weight of cargo acting automatically either in loading or discharging. Cargo can be lowered to deck for examination or weighing at any point of transit, and as many as four sets of gear (or more if length of hatchway permit) can be worked at one hatchway. The block shells are made in wrought steel, with in-Furness H.M.S. Doris, being the second of the two twin second-class cruisers which they are at present building for Her Majesty's Government. She is exactly a sister ship to the Juno, launched a couple of months ago, a full description of which appeared in the MARINE ENGINEER at the time. The launching ceremony was performed by the Hon. Mies Hood, daughter of Admiral Lord Hood, of Avalon. The launch, which took place on a very stormy day, was perfectly successful, and the Vessel was afterwards docked and placed under the 100-ton crane alongside the Powerful and the Juno, where she will receive her engines, boilers, and general fittings. Subsequently to the launch, Mr. Adamson, the managing director of the Naval Construction and Armaments Co.. proposed "Success to H.M.S. Doris," and referring to the new Naval programme, said: "The First Lord had mentioned that the vessels now building, and those to be built under the new scheme had to be finished in about three years. The shipyards in this country were capable of doing this and a great deal more if they could get the chance. He read an interesting article the other day in a newspaper which reported very closely on all nautical matters, comparing the strength of the Navy at the present time with its strength about six years before the Naval Defence Act was passed, and showing by figures that the stret gth of our Navy had been doubled during this time, not only in the number of ships, but in their power and their speed, and so on, and he had no doubt if it was required to again double the Navy they could do it in a comparatively short time. He would not detain them any longer but he hoped it would be many a day before the Doris was called into action; but there was no doubt if that time ever came she would be found qual to the work, and would uphold the honour of her country and be a credit to her builders." Mr. Adamson then proposed the health of the Hor. Miss Hood, and in reply, Admiral Lord Hood beş ged to thank them most heartily for the kind marner in which they had received the health of his daughter. He could assure them that it gave her the greatest pleasure to perform the ceremony of christening to the cruiser which had been so successfully launched that day. He was quite sure that the rapid and most satisfactory manner in which the Doris and her sister ship, the Juno, and also that magnificent first-class cruiser, the Powerful, in addition to many other war vessels built there, all of which reflected the very greatest credit on the Barrow Co. If this country happened at any time to be engaged in war, these vessels, with their high speed and great power, would prove of extreme value in assisting to protect our sea-borne commerce, which was far greater than that of the whole of the rest of the world combined, and so retain the prosperity of the British Empire. Now he considered it a point of very great importance that in addition to the royal dockyards they had in this country such thoroughly competent private shipbuilders as the Naval Construction and Armaments Co., and others in different parts of the country, who possessed the power and ability to greatly and rapidly increase the strength of the Navy, and if an emergency should arise such as often happened from sudden and totally unexpected circumstances such as had hap; ened the other day, when the nation was thoroughly awakened to the absolute necessity of this country maintaining her command on the sea, that emerge.cv could be met. They had not only to protect their vessels in 11 parts of the world, but the very extensive British Empire as a first-class Power depended upon the Navy. He thought it was a wise policy that was adopted by the last two Governments in strengthening the Navy, and he was glad to see that the Navy at the present time was now in a better preparation for war than it had ever been previously in his recollection. When they looked at the manner in which foreign navies were increased, and were still being added to, he felt that if Britain had to maintain her command of the sea much still remained to be done. He was thankful to read in the programme of the Estimates of the Lords of the Admiralty, laid before the House of Commons, on the previous night, that it was proposed to increase the Navy by five first-class line-of-battle ships 13 cruisers, and 28 torpedo boat destroyers. Of these vessels, three battleships and two cruisers only were to be built in the Government dockyards, and the rest were to be built by contract. He hoped, and he was sure all those present would join him in thinking, that a fair proportion of these vessels would be ordered from the Naval Construction and Armaments Co. In conclusion, he could only express his own feelings and those of everyone present when he wished success to the Naval Construction and Armaments Co. Admiral Boys said they had just heard from Admiral Lord Hood an exposition of what was the position of the Navy, and no one was better able to judge of that than Admiral Lord Hocd, who had been for so long connected with the Admiralty. In the name of the Naval Construction and Armaments Co., he had first to regret the absence of the Duke of Devonshire, who, owing to his exalted position in the Government, had necessarily given up the chairmanship of this company. They all regretted this, and Barrow people, who knew his Grace perhaps better than he did, but they were in hopes that in a very short time the chairmanship would be filled up by a very capable gentleman. Now, with regard to the Doris, so successfully launched that day, he thought it might interest some of them to know what was the meaning of the word. He confess d he did not know, but he took the trouble to make some inquities, and had found out that Doris was a marine divinity. She was the daughter of Oceanus and Thetis, and the mother of Nereides. The Latin poets sometimes called the sea Doris, and he presumed this was the connection between the British frigates and the name of Doris in the past and the sea itself. He found in 1798 a British frigate of 36 guns captured on the coast of Ireland a French frigate, Hoche, and consorts. In 1803, they found the Doris captured a French lugger, which kept up a running fight for seven hours. In 1806, the same frigate was wrecked on the coast of France, while in 1 20, a 42-gun frigate of the same name was building at Portsmouth, and he had not heard much of ber since. Probably she was broken up. These were all wooden ships, but the ship they had launched that day had very little wood in her. She was built of steel and iron, and as Mr. Adamson had told them, was five times larger than those he had mentioned. She had been launched by a lineal descendant of Admiral Lord Hood, of great naval fame, and the daughter of his friend, Admiral Lord Hood, to whom the Navy owed much of its efficiency, owing to his connection with the Admiralty and his knowledge of the naval service. The Doris had been put into her natural element by the daughter of a family famous for its great deeds, and the occasion gained importance from the fact that a Hood had done ar other good work in the direction of improving the Navy. He concluded with complimentary references to Mr. Gowan, Mr. McKechnie, Mr. MacGregor, Mr. Buchanan, and the other lieutenants of Mr. Adamson, who con. tributed so much to the success of the Naval Construction and Armaments Co. HIS BLUE ASBESTOS. material having all the valuable properties of ordinary asbestos as a refractory and non-heat-conducting substance, has certain unique qualities of its own. It is blue in colour, is considerably lighter than other asbestos, and the fibre is longer and stronger. It is found in Cape Colony on faims acquired by the Cape Asbestos Company, Limited, of 8, Minories, London, EC., which company has been formed to develop this useful mineral and bring it into general use. By special treatment and machinery fine wool is obtained from it of quite half the specific gravity of the finest wool obtainable from other asbestos, and so tenacious and pliable that it can be spun into very fine yarn of great tensile strength eminently adaptable for weaving into cloth, or for netting, twine or ropes, which are uninflammable, rot and acid-proof, and unaffected by atmospheric or climatic influences. It is most probable, therefore, that this blue asbestos will open markets for applications in many ways where ordinary asbestos has been unsuitable on account of insufficient strength. We are, how |