foremen of the various departments at Enfield, have won not only "golden opinions," but more substantial rewards for valuable alterations and modifications suggested and made by themselves. To mention one of these as carried out to practical use by Mr. Hayes, we may adduce that pertaining to the "swivel," which is a link to connect the "main-spring" with the "tumbler" of the rifle. Swivels are made complete, thanks to this gentleman's skill, by machines, from bars of in. steel; and all are so perfectly manufactured that they inevitably fit a test-receiving gauge. Of the."tumbler" and "bridle" machinery it would be difficult, without drawings, to give clear explanations. It comprises a simplification of the principle of the Rose engine, and does not require in working the attention of skilled workmen. Since the appliances produced by the tumbler and bridle machines are of a very minute and delicate description, it may be imagined that much patient ingenuity was exercised in perfecting them, and this is true. At the rate that the Enfield rifle, of the pattern 1853, is being made, these little improvements, moreover, are great enough in their consequences to save fully £2,000 per annum to the country. power. From the large room, in which multifarious operations are going on with unflagging regularity, one passes forward to the Smithy; and here again machinery has been brought to bear with wondrous precision. Everything prepared in this department is touched more or less by machine From this commodious and convenient apartment doors open into all the following:the tool-department, where all tools are made and repaired; the hardening-room, where all the bayonets, main-springs, sear-springs, and ramrods are tempered; the polishing-room; grindery; and various places of comparatively minor importance. A pair of 40-horse power engines, fitted with Fairbairn's expansive valve motion, drive the whole of the machines, whose "name is legion," in the above-named branch of the Rifle Factory; On the opposite side of a basin or mill-head stands another building, parallel with that mentioned above. This is of extensive dimensions, and two stories high; and here the barrels are manufactured. Combined steam and water power MAJOR RHODES' PATENT TENTS. Rhodes. After the tent had been fixed on Wed nesday afternoon, ten of the portable bedsteads in as through a sieve. Major Rhodes' hospital and, whereas in the present tents there are about tent can be pitched by eight men in 12 minutes; has only about 40 pegs and 12 ropes to secure it, 150 pegs and 70 ropes to each, the new invention there being no necessity for the men to turn out in the rain during the night to slack' the ropes that duty has to be performed by sick patients." as with the present tents-a serious matter when The advantages of Major Rhodes' tents over those of the Government may be briefly noticed. the Government hospital-marquee, and its cost is His hospital tent weighs about 112 lbs. less than about £3 under the Government contract price. The ventilation is most efficient, and subject to the control of the medical officer-impervious to wet, and the strong rays of the sun-can be pitched in 12 minutes by 8 men. The Hanove Northumberland, about ten miles north of the small class of vessels could trade to that port, and It is well known that there is a very heavy sea on this part of the coast; and that this must be water east and north is taken into consideration, the case will be obvious, when the great reach of Denmark, which are distant from 400 miles to 500 miles. But it is not so commonly understood that the nearest land being the coasts of Norway and gales spring up with a suddenness which increases in progress. It is necessary to note this peculiarity, the peril to men, and the risk of injury to works the work as originally designed. For a length of because it increased the difficulty of carrying out in this portion of, what is now, the harbour. a mile the river was exposed to the action of the sea, and it followed that no vessel could then lie Along the seaward side of the river there is a rocky reef, and upon the base thus provided by nature the breakwater has been erected. The is used in giving motion to the machinery in the barrel department; and this consists of a 25-horse rian Government (who have practically tested length of 1,800 feet was constructed, entirely of work was originally intended to be, and for a power condensing engine, with one 20 and one 25-horse breakwater wheel. With regard to the prime cost of a finished Enfield rifle of the approved 1853 pattern, it may be said that it is about £2 5s. It is a most serviceable weapon; and, from the extreme accuracy with which its parts have been fitted, and the power of interchanging them, it has an advantage over all hand-made guns. A defective part can be replaced at once without fitting. When all the component parts have been carefully tested by viewers, or inspectors, especially kept for the purpose, and who have a thorough knowledge of their duties, it is next to impossible that there should be differences. In fact, so wondrously true are all the machine-prepared parts of the rifle to each other, that a workman will take up the requisite pieces indiscriminately from boxes full of them, and put a rifle together before your eyes in three minutes! From fifteen to eighteen hundred rifles per day of ten hours are at present being finished at Enfield Factory, and this gives (nearly) an average of one rifle completed from the material every two minutes, and made fit for shooting down an invader! Altogether the number of persons employed amounts to somewhere near 1,500, and the offices and stores are admirably arranged. Colonel Dixon, of the Royal Artillery, a most persevering and exemplary gentleman, assisted by J. H. Burton, Esq., an American, and Chief Engineer, have the control of the entire establishment, which is conducted, so far as we can judge, in a most efficient manner. Looking at the state of affairs across the Channel, Government and people here may well leok also towards Enfield. this tent) pronounce that Rhodes' hospital tent affords the best shelter hitherto obtained in camp stone; but a failure in the supply of material led tal marquee, 30 feet wide by 14 feet, and 14 employ timber and stone, after the manner hospitals, &c. The price of a Government hospi- by Figs. 1 and 2. to a change, which has resulted in the work shown Mr. Abernethy proposed to feet in height, is from £33 to £35, and weighs (in adopted at Boulogne and Calais, and furnished a latter weight includes 4 ground sheets.) It affords tractor for the work, being aware of the imposthree packages) from 507 lbs. to 652 lbs. (the design similar in outline to Fig. 1. As the conaccommodation for from 18 to 20 patients. Major sibility of obtaining, on the site, stone suitable Rhodes', 20-feet diameter, field-tent cost £24, for facing, and seeing that during very high viz. about £12 cheaper, and weighs (in 2 pack-tides there was great risk of damage to the open ages) 230 lbs., viz. 277 lbs. less than the Govern- end, which had already been injured several times, for from 18 to 20 patients. Two of Major Rhodes', to carry out Mr. Abernethy's views; and after a ment hospital marquee. It offers accommodation the author gladly undertook to do all in his power 20-feet diameter, field tents can be pitched by good deal of consideration, the forms shown in 4 men (in about 8 minutes for each tent), on only one Government hospital-marquee; and served that those portions of the breakwater about the same space of ground as is requisite for with entire success some time ago. Figs. 1 and 2 were arranged, and were erected further, from 10 to 14 men require from 15 which are illustrated by Figs. 1 and 2, consist of It will be obto 20 minutes to pitch the latter tent. Major a framework of timber, filled with stone, and arRhodes' tent provides detached accommodation ranged as follows:-First, there is a sole piece for 24 rifles, 24 sets of accoutrements, and 21 resting on the ground. Upon this sole are raised knapsacks, with a perfect system of ventilation; two uprights, the one next the sea being supported in which very important points the Government by a strut from the sole piece. Cross-bearers, or hospital marquee is deficient. Irrespective of cost, half-balks, embracing the uprights, carry the road&c., it results that by adopting Major Rhodes' way above; and this is protected by a simple tents into the service, healthy shelter can be pro- handrail. The frames thus formed are placed at vided for about 45 men, allowing the same amount of transport as is at present necessary for conintervals of 10 feet from centre to centre, and veying only one Government hospital marquee, are tied together, longitudinally, by walings, two which latter only affords accommodation for 20 by the open planking, the space contained within on the sea face, and one on the river face, and also men; thus showing a clear saving of more than which is filled with rubble-stone. one hundred per cent. in cost of transport, which, that, in the first section, Fig. 1, this space is triIt will be seen with an army in the field, would be a very great angular, the planking on the river face being on relief to the Commissariat Department. the strut. partly to provide a sloping surface, and to leave The object of this arrangement was, of the proposed docks, for the purpose of dethe river-uprights isolated, opposite the entran ee stroying, as much as possible, the swell which We now learn that the officers appointed to examine Major Rhodes' tents at Chatham are about to report most strongly in their favour to the Commander-in-Chief. passes up the river. In the second section, Fig. 2, the exposure, and consequent strength required, being greater, the planking was put upon the river upright, and the whole space was filled with rubble, and was covered with an open flooring of horizontal timbers. The work has added more than 4,000 feet, in length of the river, to the harbour, where there is still-water; and not only effectually breaks the waves, but it acts as a training wall, to direct the current, and to confine, and to intensify within the new limits, the action of the tidal scour. During its erection there was no risk of injury, and no part of the timber-work has been breached, although the weakest portion has been exposed, for more than two years, to as heavy seas as were ever seen on that coast. The cost of the work has been, on an average, about £10 per lineal foot. The timber has all been creosoted, and bids fair to resist decay for many years. In the case of the portions of the pier just referred to, the site was either dry, or nearly so, at low-water spring tides; but the line upon which it was to be continued led into a depth of 5 feet, or 6 feet at the lowest ebbs, and about 22 feet at high-water spring tides. From this arose the necessity for a change of plan; but in arranging the breakwater, so far as hitherto described, the author's attention had naturally been turned to the question generally; and Mr. Abernethy having suggested that he should attempt the application of timber to deep-water sections, the author considered the subject, and, as early as January, 1857, succeeded in attaining that object, having then designed deep-water sections very similar to those to be described. quently no waste. It will be seen that an excel- The round ends, at the entrances to harbours, FACILITY OF CONSTRUCTION. Before entering upon details under this head, the author claims for his improved arrangements one important advantage, viz., that the work is not liable to be breached during erection. Those only who have had to contend with the sea can appreciate this risk; for although every precaution may be taken, still, in the case of vertical walls, of the ordinary kind at least, there is great danger during erection. The stone wall at Blyth, for example, was repeatedly damaged, but no part of the new construction has ever been breached, although exposed to a heavier sea; but, even in in sliding-ties, or by piling. These piles may be driven, or screwed, the sliding-tie forming a guide for the foot of each pile. In driving piles the author has placed the shoe on the corners of the piles which are exposed to the greatest pressure, and are most liable to abrasion. If screws are adopted, the author has designed an arrangement which, he thinks, would cost less than Mitchell's screws, and which is as follows:-The angles of the wood being removed, a thin Tiron is heated, and wound spirally round the lower end, an i this being cooled, shrinks and grasps the wood, like the tire of a wheel. The advantage of this plan is its cheapness, and the strain, instead of being concentrated, as in Mitchell's piles, upon the short piece of the pile embraced by the iron socket, is distributed over a considerable length of the balk. It would be tedious to go further into detail upon such points. It may suffice to say, that no system of piling can be compared with the plan of first sinking frames, for cheapness and speed of execution, and in hard ground piles are inadmissible. The progress at Dover is said to be 100 feet per annum; and, as the breakwaters at Alderney, Portland, and Holyhead have each been about ten years in hand, the systems pursued at those places do not appear to secure rapid execution. In this particular it is thought a saving would be effected by the new arrangements; and as an illustration of what can be done, although of course on a comparatively small scale, it may be mentioned that of the Blyth work 130 lineal feet have been erected in five days. POWER OF THE WORK TO RESIST WAVES. It has been said that the timber-faced work cannot be breached and broken up in detail, that it must go as a whole-in fact, be overturned bodily; and it is now necessary to ascertain what amount of force would effect its destruction, which, unlike the case of most stone piers, is readily calculated. In the section designed for deep water, The author divides these works into two classes; stances in which the permanent work has not been the power of the sea to overturn the work would much injured, the staging has suffered; whilst at be represented by the statical pressure of the water rising against the parapet, and the power of resistance in the work by the weight of the stone, less its displacement-the timber having no buoyancy. Proceeding upon this principle, and taking the 10 fathom section (Fig. 6) as an example, it is found that the stability is double the greatest force which could be brought to bear upon it. those intended for deep water being wave reflectors, and those for shallow water wave breakers. Excepting the wave screen, the reflectors and breakwaters are of a similar character, and consist of a timber casing filled with stone. The stone hearting constitutes the power to resist removal as a whole, and the timber facing secures the stone from being disintegrated, or carried away in detail; so that if the work is moved it must be bodily. Further, the work is so connected together, that each part supports its neighbouring portions: the importance of this will be obvious when it is considered that waves seldom strike any great extent of surface at the same moment. A marked peculiarity of the arrangement is, that there is no tie between the work and the ground. It simply rests on the surface, and the stability depends wholly upon its weight. The author is opposed to the idea of piling the face, and filling in behind lbs. or 10 lbs. of creosote per cubic foot materially ings, both on its ascent and descent, and little if In the arrangement proposed, no stone of a high, class is required, and no dressing. With respect to the timber, it is easily procurable at any port, and it is all converted on shore, the frames being put together complete, and then floated to their place. It might be thought that, in very deep water, the frames would be difficult to manage; but the experience of the author leads tate to undertake the erection, even in comparahim to a contrary opinion, and he would not hesitively great depths. With reference to this point it should be remembered that the addition of 9 It has been stated that waves travelling into shallow water must break, and in situations where it is necessary to provide a protection under these circumstances, a wave-screen, such as is represented in Figs. 8 and 9, is to be preferred. It will towards the sea, so that the waves will run up and be observed that the screen consists mainly of a grating of timber, supported on piles, and inclined the water will drop through the transverse open any will return to the foot. In the case of a stone slope, the whole of the water which has been pro with stone, not only because it is difficult and expensive to pile in a sea-way, but because, in his reduces the floating power of the timber, so that the following is a statement of the buoyancy of a estimation, it is false in principle. For the piles 10-fathom section (Fig. 6). Supposing the whole jected up the slope runs back, and it is by this would necessarily bend before they took any ap; timber immersed, the total buoyancy would only recoil that the great damage is done. preciable part of the strain, and before they could deflect, the stone backing must have been moved. Piles may, however, be used in some cases, as a convenient method of filling the space between the frames, for the purpose of keeping the stone from spreading; but then, on the author's plan, these piles would be driven subsequently to the erection of the frames, which constitute an efficient staging from which to drive them. be 15 cwt. per foot run of the breakwater; but as The dropping through of the water has another important advantage. Suppose the oscillation of the water passing under the toe of the screen to cannot be more effectually combated than by the be only partially destroyed, the remaining motion vertical and continued fall of water through the screen. Moreover, the effect of the blow of the ings between the planks. There is, however, a waves upon the slope is diminished by the openlimit to increasing these spaces, for if they are too wide the water falling through, instead of neutralising the existing oscillation would produce a fresh one. The longer the slope the greater the secondly, the joints are covered by whole timbers: ties, which are simply balks of timber with chocks surface over which the force of a given wave is thirdly, each piece is proportioned to the work it between them embracing two frames, and being distributed, and the less the horizontal strain prohas to do; and lastly, there is such a variety of secured together above water, they are slid down duced; but if the slopes were too flat, the effect size, as to admit of average cargoes being wholly would be that the wave would run up and fall worked up without waste. The faces are so tied inwards as to prevent the rubble from being forced out; and whilst the interstices are sufficient for the free escape of air, there is, after a short time, no motion amongst the stones, and conse-meeting. Other leading features are the framework is so arranged, first, that the strains are, as much as possible, taken in the direction of the length of the timbers, thus developing its greatest strength; In the direction of the length of the breakwater the frames are kept parallel by the sliding to the bottom. To obviate the employment of over. This wave-screen has a peculiarity which, in many situations, is of the greatest importance, namely, the allowing the tide or currents of the sea to pass through with little interruption, thereby preventing the silting-up of a bay, or the estuary of a river, which is a general consequence of its enclosure by any breakwater of an ordinary kind. The construction of the screen is of the simplest kind. It consists of piles at considerable intervals. To these the main timbers are secured, upon which the grating of planks is laid. It will be observed that these planks are tapered in cross section, making the lower edge thinner than the upper edge. The object of this is threefold. First, it diminishes the shock of the water on the planks as it rises; secondly, it ensures the interception of the water on its descent; and thirdly, it gives to the main timbers a secure hold of every plank. DURABILITY AND COST. There is another material which the author is at present testing, but a sufficient period has not elapsed to prove its qualities. The author is of opinion, that there can be little doubt that the timber would last twenty years; but, without speculating further upon this point, it will be sufficient to show, that the difference in first cost between ordinary stone breakwaters and the new arrangement, is so great as to leave an ample margin in favour of the timber system. The 10fathom section, Fig. 6, would cost, complete, about £70 per lineal foot; whereas the stone break. water at Alderney is said to have cost £190 per foot, and that at Portland £150 per foot. cost of these, as compared with the timber system, for a length of say 2,000 yards,-about the length of Portland and Holyhead,-would stand as follows: : £420,000 900,000 1,140,000 The Timber System, Fig. 6... Portland... Holyhead, unknown, but believed to have cost a great deal more. Alderney... The manner in which the timber of such a work, as is shown in Fig. 6, would be renewed, would depend on the nature of the bottom. If it was clay, or sand, for instance, the face might be simply close piled, and by the application of the new arrangements for piling, this would not be an expensive operation. But if the bottom were hard, than a cradle filled with stone might be lowered and thus the face would be renewed. This cage, as it may be called, would have several hundred tons of stone in it, and this would represent the weight of the smallest pieces of the face. These two stand in such intimate relation to each other, that it is proposed to consider them together. The first question which arises is, how long will the timbers last? To this it is not easy to give a definite reply. The chief enemies to be encountered are the Teredo Navalis, or great worm, and the Limnoria Terebrans, or surface worm, as it is often called, but which, in fact, is a species of shrimp. The operations of the Teredo are said to be confined to the space between lowwater and the bottom, as they cannot exist out of water, whilst the Limnoria attacks the wood chiefly near low-water, and particularly at the surface of the ground, in cases where the bottom is dry at low tide. There is no doubt that unprepared fir-timber, excepting the more resinous pines, would in some cases be destroyed in a few years by these animals, and it is said that even greenheart succumbs in time to their efforts; but Finally, it remains to be shown, that even if the there are instances which indicate great durability. new arrangements be regarded merely as a means The piers at Boulogne and at Calais may be men- for forming the back-bone, as it were, of a more tioned as having stood for many years-a part of permanent stone structure, it is the best and the latter, which is of oak, being above seventy cheapest way of attaining that object; for, viewyears old. But the true question is with regarding the timber only in the light of a temporary to the durability, not of raw, but of prepared timber; and the experience of the author of the process of creosoting leads to the belief that, when properly done, it will preserve timber for many years, though how long it is impossible to say, as time alone can show. staging, the following would be some of the advantages of the system-rapidity of execution; the enclosure of the harbour, and the protection to the shipping being completed years before an ordinary stone-work could be erected; and an excellent staging from which to build the stone facing, which might be proceeding at severalplaces at once, as there would be no interferencefrom the current, and no danger of breaching. Then the rubble hearting, having been exposed to the sea for years, would be thoroughly consoli-dated, and would form an impenetrable backing which is always of great importance, and from the strength of the staging very large blocks might be employed in the facing. (To be continued.) FRENCH PRIZES FOR REAPING PARIS, Friday July 23.-The competition for the prize proclaimed for the best reaping machine came off yesterday at Fouilleuse. The Emperor was present, and exhibited the greatest interest in the proceedings. Forty-five machines had been registered, but twenty-five only appeared in the field. A wide extent of harvest land had been divided in patches of wheat, rye, and barley-all nearly in equal proportion. The cutting of each patch was drawn for by lot. The machines were catalogued under two distinct heads-the foreign machines and those of French manufacture. The prizes for each division were the same-1,000 fr. and a gold medal first prize, 500 fr. and a silver medal the second, 300 fr. and a bronze medal the third. Moreover, a great gold medal had been voted as honorary prize to the machine considered the best of the whole, whether French or foreign. This prize, as well as the first in the foreign division, fell to the lot of Messrs. Burgess. and Key. Worked by two horses, its action surprised the assembly. The harvest fell before it with a precision and regularity never attained by human hand, while the quickness with which the work was executed proved an incontestable superiority over manual labour. Moreover, this machine proved itself the only one in the field capable of being worked with the assistance of only one man, and by measurement it was known that the Burgess and Key reaper could clear an hectare of ground in an hour and a half. Cranston, of London, obtained the second foreign prize. The first French prize was awarded to M. Mazle, of the Department of the Orne, the second to M. Longitudinal section of part of a tubular boiler, with three varieties of spiral heat diffusers, shown within the tubes, the central tube has a ferrule inserted. Lallier, of the Aisne, and the third to M. Legendre, of the Charente Inferieure. Independently of these testimonies to physical perseverance, another prize of more importance still was voted to M. Durand, Mayor of Baruel, for the moral perseverance with which, in spite of the opposition of ignorance, he had encouraged the use of the machine in his commune, and a silver medal and a sum of 100f. were likewise awarded to the ploughman in the employ of M. Durand, for having aided his master in this undertaking. The Emperor was accompanied on the ground by the Count de Montebello, where he was received by M. Rouher, Minister of Agriculture, by Count ChasseloupLanbat, Minister of Algeria and the Colonies, and by all the notabilities connected with the progress of agriculture in France. At the close of the experiments the Emperor presented to each of the successful candidates the prize which had been awarded him, and at six o'clock left the field amid the hearty plaudits of the assembly.-Correspondent of" Morning Star." The advantages of these heat-diffusers are obvious and manifold. In the first place they are very simple, and their application does not require any alteration of the boilers now in use; and they can be inserted at the shortest notice at a comparatively small cost. Secondly, it has been proved by experiment that they are self-cleansing. Thirdly, they materially lessen the consumption of fuel. This is their characteristic advantage, and will in all probability recommend them to the consideration of engineers, railway and other companies. Upon the 9,500 miles of British railway there are now employed more than 5,000 locomotives, performing an annual mileage of upwards of 90,000,000 miles. The fuel consumed by these engines may be taken as equal to 1,500,000 tons of coke; and this quantity of fuel may be valued at £1,200,000. The introduction of the heatdiffusers to the above number of locomotive boilers would effect, at 30 per cent., an annual saving of £400,000, and involve no alteration in any of the existing arrangements. No doubt this invention will be found particularly valuable to steam navigation. A fullpowered 3,000 tons paddle steamer carries 550 tons of engines, boilers, and appurtenances, 1,400 tons of coal, and 100 tons of water in her boilers, making nearly two-thirds of her burden. It is principally on account of this vast tonnage of fuel that steam navigation has hitherto proved a commercial failure-as it is well known that no line of swift steamers can exist without a GovernDUNCAN AND GWYNNE'S PATENT HEAT ment mail contract. If, however, a steamer which DIFFUSERS. AN invention has recently been introduced whereby the steam-producing power of engines may be greatly increased. This is done by introducing into the tubes of boilers spiral heatdiffusers. By the aid of these diffusers a column of heated gas is so distributed in the tube of the boiler as to make it produce, it is said, about 30 per cent. more steam. Flames and other gaseous products of combustion in passing through the tubes of boilers now in use, impart only a portion of their heat to the surrounding metal. These productions pass with considerable rapidity through the tubes, and being æriform and bad conductors, consequently a large proportion of their energy is unproductively expended by the present mode of generating steam. The metal of the tube only absorbs heat from that portion of the column of flame in direct contact with it, consequently, the central portions of the column are permitted to escape with the smoke out of the chimney. The patent heat-diffusers now under notice break up this column, and compel its component particles to strike against all sides of the tube. In this way more heat is transmitted to the water of the boiler, and consequently more steam produced at a less cost. has hitherto required 1,400 tons of coal may, by We may add that the patent heat-diffusers are the Hon. James R. Drummond, C.B., Aide-de. Camp to the Queen, in his official capacity as superintendent, attended by the entire body of officers representing the various departments of the yard. One of the instruments was erected at either end of a long enclosed lobby adjoining the dockyard factory, when a lengthened test of messages and replies was satisfactorily carried out. The experiment was extremely interesting and conclusive as to the merits of the apparatus, the result of which was promptly transmitted to Lord Clarence Paget by special direction of the Commodore to that effect, the invention having been pronounced one of the most important of the kind hitherto produced, and likely to be productive of immense benefit to the entire naval and merchant service afloat. The weight of the instrument, which is of the simplest construction, does not appear to exceed 14lb. It represents the form of a cross, exhibiting five alphabetically marked lamps, which are worked by a process resembling the keys or notes of a piano slowly depressed, and at the termination of each sentence the lights are clouded. As regards the working of the instrument, the principal officers of the Fisgard who yesterday attended the experiments affirmed without hesitation that any boy of Her Majesty's fleet could obtain a prefect mastery of the system by a couple of evenings' study.-Naval Intelligence of the "Times." THE MANUFACTURE OF CANNON. (Concluded from p. 58.) MR. LONGRIDGE next made a gun of a thin castiron tube, with wire coiled round it. It weighed only 3 cwt., yet threw a 9-pound shot 1,500 yards. A 6-inch hydraulic press, which he had made of cast-iron three-quarters of an inch thick, with wire coiled round it with a carefully-calculated increasing strain to a thickness of half an inch, was sent to a gentleman at Glasgow to be tested; he reports that it has borne a pressure of upwards of seventeen tons per inch! One-fourth of this would have destroyed most cast-iron cylinders of treble the thickness. Time, I regret, will not permit me to describe any other of Mr. Longridge's valuable experiments. I will only mention one more experiment to-day, but that a most important one, because made by Colonel Treuille de Beaulieu, a disWARD'S AMERICAN SHIP SIGNALS. tinguished French artillery officer, and one of the Mr. W. H. Ward, of Auburn, United States of Comité d'Artillerie of France. He had a 32America, yesterday exhibited in Woolwich Dock-pounder (French 30-pounder) turned down cylinyard, by permission of the Lords of the Admiralty, drical from the breech to near the trunnions. his patent invention for transmitting messages Over this he shrunk steel tubes, accurately bored. and carrying on correspondence of any length from ship to ship, becalmed, or sailing within telescopic sight of each other on the ocean, with equal facility to that of the electric telegraph on land. The exhibition was witnessed by Commodore At first sight this looks very like my plan, but regret to say that I cannot quite agree with Colonel Treuille in his method of construction. I The steel he uses is very tough, and similar to that wonderful metal now made so inexpensively much. I have already given reasons why the metal must decrease in thickness when strained; I will now, therefore, only refer to Major Wade's experiments, which show that in every instance he tried such was the case. by the Mersey Steel Company. Like it, it can be of one length to a certain amount, could only stretched one-fifteenth of its length without break-strain a fibre three times as long one-third as ing, and one one-hundredth-and-fiftieth without losing its elasticity. Colonel Treuille made his outer tubes only one three-hundredth of their dia meter less than the outside of the cast-iron cylinder. This was about 164 English inches in diameter; the bore of the gun being about 6 inches. Now this cast-iron cylinder is thicker in proportion to its bore than any of those Major Wade tried. The outsides of his were stretched but one-eighth as much as the inside, when free to expand. I do not think that in Colonel Treuille's 32-pounder, therefore, the outside of the cast-iron cylinder, encompassed by a strong steel envelope, can expand more than one-tenth as much as the inside of the gun. Granting, even, that his cast iron can be stretched 1 in 300 without danger (which I doubt), still the outside would only be increased, even then, 1 in 3,000. One three-hundreth added to one three-thousandth would then be the greatest elongation of the steel possible, without fracturing the inside of the cast iron. Nearly one-half of the strength of the steel is thus made no use of. As it is, the gun is strong enough to resist any strain by gunpowder in a lateral direction. When Colonel Trenille first showed and explained it to me, I ventured to express an opinion that the breech would eventually be blown back, owing to the great squareness of the end of the bore in French guns. I had the honour of seeing that gentleman, however, a fortnight ago, and was rejoiced to find, as I am sure you will all be glad to hear, that hitherto neither this nor any other catastrophe has occurred. On the contrary, the gun has borne 1,000 proof-charges without the slighest injury except to the vent, which, of course, has been more than once renewed. His method of manufacture must not be confounded with that proposed years ago by General Thierry, who thought to obtain the rigidity of cast iron and the strength of wrought iron by simply placing tubes of the latter metal over one of the former metal. Guns were so made, which looked exactly like Colonel Treuille's or mine; yet they were perfect failures. The reason is obvious; the strain was not communicated to the wrought iron, as it had no initial tension, or at most only enough to give it a firm hold on the Those who argue that the strain is in the inverse ratio of the squares of the diameters, believe that the thickness of the metal diminishes as the circumference is increased by pressure from within, but that the total bulk of the metal re- | mains constant; and that, therefore, the area of the surface of metal, which would be exposed by making a cross-section through the cylinder, perpendicular to its axis, must be also constant whatever the pressure. Now, on this hypothesis even, the outside of a cast gun could not do more than one-ninth of its work; yet, in all Major Wade's experiments, the cross-section was decreased by strain up to a certain point, which proves that the useful effect of the metal must have decreased in a greater proportion than even the squares of the distance from the centre. Had I not found an account of these experiments I should have despaired of ever convincing any but persons possessing a knowledge of science that guns are at the present time being cast by thousands in such a manner that fully two-thirds of the metal in them is not only utterly useless but most mischievous, because rendering their transport more difficult and expensive; and that the extreme outsides of the present guns cannot exert one-twelfth of the power they could be made to exert. These experiments are valuable to me also as establishing the truth of another argument I used Although I think that Colonel Treuille could here on a former occasion. It is constantly ashave obtained equal strength by the use of oneserted that the pressure of the gas of gunpowder half the quantity of steel, had he made the steel amounts to ten or twelve tons per square inch of cylinders one four-hundredth part less in diameter, surface, and that its action being sudden is more still, as he actually does not make them do ten mischievons than an equal pressure applied more times as much work as if they were not in a con- slowly. As guns do bear the repeated application stant state of tension, I hope I may fairly consider of this pressure, I was told that I must exaggerate him as an authority, and a most weighty one, in their weakness. My reply was, that the shot, by favour of the principle of construction I am advo-moving directly the first particles of powder burnt, cating. leaves room for the rest to expand gradually, and that the pressure can never be so great as is said, because such pressure acting through a certain space must necessarily produce a greater velocity than we know is produced. The belief in the great pressure of the products of powder, which has been handed down to us from former generations, must now at last yield to demonstration. Major Wade burst a serviceable 18-pounder gun behind the trunnions with a pressure of 4 tons per inch. The pressure of the gunpowder must therefore have been less than 43 tons per inch, or at all events less destructive than that pressure longer applied. This is very important, upsetting all preconceived ideas of the violence of the explosion of gunpowder in the cannon now used. In larger guns the pressure of course would be greater, because the shot would acquire motion more slowly, therefore would leave less room for the igniting powder. Hence the larger the gun the greater the difficulty of getting it to resist the explosion; hence the utter impossibility of making guns beyond a certain size to fire full charges of powder without making more than one layer of interior. The difference of opinion between Colonel Treuille and myself is only as to the degree of disproportion between the useful effect of the inside and the outside of cylinders. He thinks that in the 32-pounder he made, the outside of the cast-iron part, which was about 50 inches in circumference, could exert two-fifths as much strength as the inside, which was about 20 inches in circumference; the diminution being in the direct proportion of the diameter. Now, I believe that the diminution is in a greater ratio than even the squares of the diameters; in the above case more than 25 to 4, instead of 5 to 2. The question is of such importance in deciding the necessity of abandoning the present method of making guns by casting, that I trust you will permit me to discuss it a little fully. Those who, like Colonel Treuille, argue that the strain is in the inverse ratio of the diameter, must believe that the thickness of metal remains constant whatever the pressure; for under no other conditions would one part be exactly as much elongated as another. Even on this view of the case the outside of a service-gun, which is fully three times greater in circumference than the inside, could only do one-third as much work, because an elongation which would strain a fibre metal take its fair share of work. guns, on the other hand, bear without injury the much greater pressure resulting from the use of a bullet covered with lead, and fitting extremely tight. His bullets, indeed, are made larger than the general bore of the gun, are inserted at the breech end, where the barrel is slightly wider, and are forced by the gas of the powder through the narrower part. The pressure of this gas must be enormous, because the powder must have time to be entirely burnt before the shot moves many inches, resisted as it is. How, then, does Mr. Armstrong obtain power, accuracy, great velocity, and extreme range from a pressure much greater than that which destroys Mr. Whitworth's guns? How can he use a pressure capable of giving such velocity to his bullets, that a twist not half so rapid as Mr. Whitworth uses is yet sufficient to ensure accuracy which must be seen to be credited? I will answer these questions by quoting the words in which Captain Younghusband, R.A., described the manufacture of Mr. Armstrong's guns to the Royal Artillery Institution in April, 1856 :— "A core, or internal lining for the gun, was formed of cast steel, to which the requisite strength was given by encircling it with twisted cylinders of wrought iron, made in a similar manner to gun barrels, and tightly contracted upon the steel core by the usual process of cooling after previous expansion by heat; the parts are then in that state of initial tension which is necessary to bring their entire strength into operation." This "initial tension" of the outside of the guns is, then, the difference between Mr. Whit worth's and Mr. Armstrong's, between failure and unexampled success; and it is this "initial tension" of the outer parts which I have been advocating for upwards of four years, which I have endeavoured to advocate to-day, as not only beneficial but absolutely necessary when great strength is required. It is but fair to Mr. Armstrong to state, that, judging from dates, his first gun must have been commenced long before I published my views, although after I had taken a patent and made one or two guns. We, therefore, arrived independently at the same conclusion. Though I claim to share with him the honour of the invention of the means of obtaining strength in cannon, yet the marvellous accuracy he attains, the ingenuity and simplicity of his plan for loading by the breech, the perfection of his fuze, the skilful shaping of his shell and of the inside of his barrel, the scientific way in which he secures the great pressure, guarding against any waste of it; these and many other advantages are due to him and to him only (so far as I know), and I am confident you will all join me in hoping he may receive the hearty gratitude of his country for his patient, laborious, most scientific, and most successful researches. I will conclude by taking the liberty of entreating any of you whom I have been able to convince of the truth of my views to promulgate them. I venture to make this request now, because every cannon foundry in the kingdom is busy making guns which in a year or two must be obsolete; and because, what is far more dangerous, we are planning expensive means of defending our seaports against guns now in use, against guns which we will heed no more than bows and arrows by the time our defences against them are completed. Those defences I need hardly say will be useless against cannon which can be made, and which in a year or two will be made. TOWERS OF STRENGTH. In rifled cannon this limit is reached in a smaller calibre than in smooth bores, because the resistance of the twist and of the friction prevents the shot moving from its place rapidly enough to leave room for the gas of the powder, which being thus confined exerts more power. This additional TO THE EDITORS OF THE "MECHANICS' MAGAZINE." power has been turned to advantage by Mr. GENTLEMEN,-All soldiers who have been enArmstrong, but has hitherto baffled Mr. Whit-gaged in "various wars" know that the first worth, in his endeavours to obtain good results object of an active enemy is to rush at and seize from rifled cannon. The 32-pounder and the 68pounder made by the latter were burst by the factories, &c., and immediately set to work in upon strong bully as churches, mills, pressure in the gun, though the shot was of iron fortifying them in such a manner as to cause only, and not tightly fitting. Mr. Armstrong's great loss to those who would endeavour to retake generally fortified with towers. In the event of them. All our churches are strong buildings, This was written, it should be recollected, in January last.-EDs. M.M. |