CAPTAIN ADDISON'S RAILWAY SIGNAL. It has been long since universally admitted that the invention of a signal by which the passenger travelling in a railway carriage should be enabled at once to communicate with the guard or with the enginedriver was a desideratum. Many instances have occurred in which the establishment of such a communication would have prevented the occurrence of much mischief. It not unfrequently happens that the friction of the iron axletrees of the wheels of a railway carriage produces ignition of the woodwork forming its flooring, and whilst the train is proceeding it is impossible, save by the adoption of the signal system, that the guard can be made aware of the occurrence of the fire until the carriage is actually in flames, by which time probably the passengers would be burned. "It is not until a bishop is burned that any measures will be adopted to prevent the recurrence of these accidents," said the late witty Canon of St. Paul's; and shortly afterwards the Bishop of Exeter was nearly burned to death from the ignition of the floor of the carriage in which he was travelling on a railway, and his life was saved only from the fortunate cireumstance of the train stopping at a station before the fire had spred. An accident of a similar nature placed in jeopardy the lives of Mr. Paxton and his friends during the course of their recent journey to Derby, to attend the festival which the inhabitants of that town had given in honour of their townsmen, the constructors of the Crystal Palace. It is not long since that during a night journey from Birmingham, a gentleman travelling in one of the carriages was attacked, and nearly murdered, by his fellow passenger, who was suddenly seized in a fit of raving madness, and who having nearly murdered his companion, leaped through the window of the carriage whilst the train was proceeding at full speed, and, marvellous to relate, escaped unhurt. Only last week two young men leaped from a train whilst it was in motion, one of whom was killed and the other severely injured; but their fellow-passengers had no means of communicating the occurrence to the guard, until the arrival of the train at the next station, whilst had such communication existed, the train might have been stopped, and the wounded man conveyed at once to a the carriage as to be distinctly visible to the guard, whose business it is to keep his eye constantly along the whole line of carriages. During the course of the journey, this signal was given at least a dozen times, and was always acknowledged within two seconds of the time of its exhibition. The experiment had been performed several times before any of the passengers by the other carriages were at all aware of what was going on, and had it not been that they heard the conversation on the subject which took place at the different stations where the train stopped, they would have completed their journey without being aware that any experiments whatever had been tried. The experiment with the night signal was equally successful. In the night signal, at the same time that the iron flag flies out, a hammer falls upon a blue light, fitted up with a percussion apparatus, which at once ignites the light, and thus points out the carriage. The success of these experiments was complete, and we congratulate Captain Addison on having invented a safe and simple signal, which meets all the objections that have been made to the signal system, whilst it realises all its advantages.-Evening Sun. BIR SAMUEL BENTHAM'S EXPERIMENTAL VESSELS. * Entertaing the opinion that we are ignorant of some of the most important points of consideration in naval construction, it will not be supposed that I wish to convey the idea that Sir Samuel Bentham thought the experimental vessels he had constructed were models of perfection; but as the form of those vessels was referred to in his communications to the Admiralty as having been successfully adopted, as the draughts of them, as given by Charnock, are in many respects inaccurate, and as their form still differs materially from that of other vessels, short descriptions of their form, taken from the original draughts of them, are now furnished. By these draughts, it appears that the Dart and the Arrow were 128 feet 8 inches long, whilst their breadth in midships, moulded at the deck, was only 33 feet; though the sides of these vessels tumbled out, instead of retreating inwards, thus differing essentially in the proportions of length to breadth from * Mech. Mag., March 30th, 1850. vessels as theretofore constructed, but which afforded examples now very generally followed in vessels of every description. Indeed, the advantage in point of speed gained by great length in proportion to breadth, has been so marked that, at the present day, the proportions exemplified in those sloops are frequently much exceeded. Another remarkable peculiarity of the experimental vessels was their sharpness at and towards the head; this innovation has also been frequently adopted. The sharpness, however, extended no farther than to within about 12 feet of the middle in length of the vessel; from thence it took a form barely curvilinear, and continued nearly straight to the middle, from whence the form slightly receded for another 12 feet aft, at which point it much resembled that of the fore part, though not quite so sharp. By giving great breadth for so considerable a length in the middle of the vessel, internal space was afforded for stowage, for accommodations for the crew, much deck-room for rigging and manoeuvring the vessel, and for working the guns. How far flatness of form for a great length fore and aft of the middle traverse-line may contribute to speed, or may retard it, remains yet to be decided. The question was to have been an early object of the experiments commenced in 1830; besides what is said in Sir Samuel's papers, in Nos. 1476 and 1477, experiments for its determination are indicated by the sketches engraved in No. 1295 of the Magazine. These sketches exhibit different lengths of straight-sided models, intended to be interposed between other models representing different forms of heads and sterns of vessels. His experimental vessels, which were nearly straight for so considerable a part of their length, were swift, and remarkably good sea boats, evincing the greatest superiority in bad and blowing weather his serpentine or vermicular vessels, constructed in Russia, were remarkable for speed, though the middle links were all of them straight, those at the head and stern being the only sharp ones; it must, however, be noticed that the serpentine vessels were used only in rivers, he not having remained long enough in the south of Russia to try the effect of such a form in agitated seas. The Dart, the Arrow, and the Netley were alike in their transverse sections, their bottoms in midships nearly portions of circles; they were originally furnished with sliding keels, and when they were removed a few inches of false keel were given them; the Millbrook, though not designed for sliding keels, was much of the same form; the top sides of all of these vessels tumbled outwards; so did those of the Redbridge and Ealing, but these schooners instead of being nearly flat bottomed, were very sharp towards their keels. A difference so very great in the form of the lower part of those vessels might have been expected to have marked itself in their respective degrees of speed, and in other properties; yet no difference in their qualities as fast-sailers and good sea-boats was observed during the many years they were constantly employed in severe service. Their power of resisting strains from the unintermitted firing of ordnance of great calibre has been already noticed in No. 1325 (p. 635), of the Mechanics' Magazine; so have many examples of their other good qualities been specified in the first part of the United Service Journal for 1830, p. 337. Many other still existing documents might be added to the extracts given by that journal in proof of the superiority of those vessels; but it seems needless to do so, since those may suffice, and its pages be so easily referred to; in this instance, it may be said, much profit might be derived from them by persons seeking examples on which to ground improvements in naval archi tecture. A diagram, showing a midship section Midship Section of "Redbridge" and "Ealing." and as to the economy exemplified in these vessels, it cannot be more forcibly evinced than it was by the offer of a shipbuilder habitually contracting with the Navy Board; he was willing to build a frigate on Sir Samuel's plan for 87. 10s. a ton; two-thirds of the then contract price and a vessel for carrying water in bulk planned by Sir Samuel, but which was strong enough to admit of being heavily armed, was actually built by contract at Plymouth for 67. 10s. per ton. M. S. B. ON THE CONSTRUCTION OF LIFE-BOATS. Sir, I have read with much gratification the Report upon life-boats, occa sioned by the patriotic and humane steps taken by the Duke of Northumberland to promote the means of saving human life in cases of shipwreck, and the encouragement given by his Graces's munificent premium offered for the best model. The Report appears well and ably drawn up in adverting to the many points to be considered in a life-boat, and directing attention to these considerations. I have read, also, a letter in the Hampshire Advertiser, of the 18th October, signed "A Voice from the Goodwin," with much interest from the well-meant and many sound remarks contained in it. Some of the observations appear a little at variance with what have been considered requisites, such as buoyant sides: and the construction I am about to call attention to-namely, the flat floor,-is particularly objected to. These objections I consider to arise from not having studied the qualities of the build proposed, and the means that may be provided to obviate the grand objection to a flat floor-namely, that of leeway. I would observe, that the bend construction appears to be the chief or only style of build thought of for life-boats. No one will gainsay that such construction is adapted for boats generally for "United Service Journal," 1830, p. 336. The whole of this communication of Sir Samuel's, "On the diminution of expenditure without impairing the efficiency of the Naval and Military Establishments" seems well worthy of perusal. The articles that have appeared in the Mechanics' Magazine relative to Sir Samuel Bentham's ideas as to naval construction will be found in the following Numbers :-No. 1294, 1295, 1305, 136, 1323, 1325, 1227, 1330, 1331, 1337, 1363, 1365, 1371, 1390, 1392, 1400, 1401, 1404, 1405, 1407, 1409, 1419, 1470. lightness, strength, and safety, and ordinary purposes. But for life-boats we have to consider the form best qualified for that particular service; and I beg leave to submit the advantages of a boat flat-floored similar to a Thames punt. Such a construction possesses the greatest power of flotation from its extent of surface; and its bearing is the greatest possible, all the breadth surface being brought to rest on the water; and from the same cause, also, there is the least liability to upset. It may be observed, that there is. scarcely an instance of a punt being upset on the river. This is a very different thing, however, from the waves of the sea and the rough weather of a storm; but of these more presently. I will now first point out the advantages of the flatfloor construction for the purposes of a life-boat. Fig. 3. The flat floor offers, besides its stabi lity, the best form for internal flooring of cork,-which is the most desirable material to form the bottom, not being endangered by staving, and acting as floating ballast against air-vessels above, at the sides, ends, and under the thwarts. The cork floor being flat, will be placed with the greatest advantage both for floating and ballast, from its exposing a large extent of surface, and its weight being placed at the lowest position possible. A cork floor of 6 inches depth would not immerse with the crew more than or near that depth, and therefore either with scuppers, or delivering tubes, would enable the vessel to free herself easily of water when shipped. The quantity of cork should be regulated by what would float the weight required of the boat and crew. Weight of cork taken at 12 lbs. to the cubic foot would give near 100 cubic feet, and 72 cubie feet would be sufficient for the support of a crew of eight men, |