The

purpose named perfectly. This is Lee & Morgan's instantaneous self-closing water escape port. great objections to the ordinary bulwark port are the constant flapping and banging that takes place when the ship is rolling, and its liability to admit water from the outside. The only practical use for bulwark ports is to free the decks from water coming over the bulwark or bow. The illustration clearly shows how this is accomplished, and in a very simple manner. Instead of hanging the port on the outside by means of hinges as in the ordinary way, this port is hung on the inside of the bulwark by means of a long bolt and four sockets. The self-closing action is effected by two spiral springs, made from a special brand of copper to prevent corrosion. By the action of the springs the port remains firmly closed during the rolling of the vessel, and can only open through pressure of water on the inside. The water, in a word, forces its way out, and the pressure being removed, the port again becomes firmly closed. All outside hinges, snecks and rings being done away with, the chances of the port being carried away and of other damage being inflicted are reduced to minimum. These ports cost about the same as ordinary ports, and have recently been fitted to the large Australian liner the s.s. Narrung and also to the s.s. Effective, the s.s. City of Rochester, &c., &c. The latter vessel is engaged in the coasting trade and has been through much stormy weather lately.

The port has therefore had a severe testing, and it has been amply demonstrated that it is capable of doing all that is claimed for it.

The manufacturers of this speciality are Messrs. John Morgan & Sons, South Dock, Sunderland, and the sole agent for the North-East Coast, is Mr. J. W. Donovan, 3, Norfolk Street, Sunderland.

the "true" diagrams of the engines, and to inform us that, due to cur being content to accept the diagrams as drawn by the indicator, engines are allowed to work with an overbalancing lead on the high-pressure engine.

Mr. Henderson says his attention was forcibly drawn to the matter when designing "a cross-compound, direct-acting, pumping engine without a shaft," which was a case where absolute equality of power of the two cylinders was imperatively demanded. When coming to triple-expansion engines, he says a ready way to understand the working of such, is to conceive the three pistons superimposed upon one another, as shown in Figs. 3 and 4, and considered as one piston.

Revised calculations for proportioning the cylinders of a compound," and of a triple engine, are given, but not here repeated. Mr. Henderson believes he is the first to point out that the loss from back pressure is reduced to one-ba.f in a compound, and to one-third in a triple, of that encountered by a simple expansion engine of the same power.

As will be seen, the above article makes no attempt to prove its statements further than by several very loose analogies, and evidently all who accept its teachings either discredit, or throw to one side the principles of "mechanics," the only way which presents itself to disprove its statements to such is by simple experiment, which, if conducted in our imagination, may appeal

to the understanding, or, if carried out materially, will force the acceptance of the truth as natural phenomena.

If a cylinder be placed horizontally, so as to reduce the discrepancies as much as possible, due to neglect of friction and other refinements, and be fitted with two pistons, which will divide the cylinder into three compartments, each of which is to be fitted with a pressure gauge, steam-admitting and exhaust arrangements; the pistons to have individual rods, working one through each end of the cylinder-(the pistons and their rods may here be considered perfectly rigid bodies)—outside which ends each rod is to be fastened to a fixed spring indicator, so that the magnitude of the load and its direction of each piston may be seen at any time. It is found that by admitting steam to the centre compartment, while the end gauges stand at O lbs., that both pistons tend outwards; and if the three gauges stand, say, at 0 lbs., 100 lbs. and 0 lbs. respectively, the load indicators will show loads of opposite direction, but both equal to 100 lbs. by area of piston. Thus the steam pressure acting on the pistons which are at the ends of this cylindrical column of steam is fully effective, and loads each piston with an outward load, which is "balanced" by the spring of the indicator at either end. Had the pistons been fixed to an ordinary through rod and these two pistons' loads been sustained by the cohesion of this length of rod between the two pistons, then would each load be separately "balanced" by this force which the particles of the rod are endowed with; for if the rod were severed the pistons would fly outward, owing to the loss of the “balancing force to each exerted by the rod's particles. Thus it is wrong, strictly speaking, and misleading to here speak of the one piston's load "balancing " the other piston's load.

Returning to our engine, which we left with gauges showing 0 lbs., 100 lbs., and 0 lbs., while so loaded admit steam at the right-hand end till its gauge also stands at 100 lbs., the loadindicator for this right-hand piston will now show no load, while the other piston's load is unchanged, thus the "balancing" force of the indicator spring has been transferred to this newly-admitted steam, which has loaded this piston with another load equal in magnitude, but opposite in direction, making the effective load of this piston nothing, as is shown by its spring indicator. Had the ordinary through rod, previously mentioned, existed, the "balancing" force it exerted on this piston would be transferred to this newly admitted steam, while its balancing" force on the other piston would be transferred to the spring of that piston's load indicator. Thus, whether this rod exists or not, we have an effective load on the left-hand piston of 100 lbs. by area of piston, while the right-hand piston has no effective load.

By Mr. Henderson's teaching the effective load on the righthand piston is 100 lbs. by area of piston, and on the left-hand piston there is no load, for it has no effective area, since when the area of the right-hand piston is outlined on it, there is no marginal ring left, which results are not in accord with the above experimentally-obtained facts, and consequently they are wrong.

Returning again to our engine, let more steam be admitted to this right-hand compartment, till the gauges show respectively 0 lbs., 100 lbs., and 200 lbs., then will the right-hand load indicator show the same magnitude of load as it did when the gauges stood at 0 lbs., 100 lbs. and 0 lbs., but its direction will be reversed, so that we now have both indicators showing for their individual pistons, loads, equal in magnitude and direction, of 100 lbs. by area of piston; the collective effect of which, of course, is 2 (100 lbs. by area of piston), which would have been indicated at the left-hand, and sustained by its spring, instead of at and by the right-hand indicator's, had the through rod, before referred to, existed, and the load of the right-hand piston been transferred from its indicator spring to it, in accordance with the method of treatment adopted, this rod would, in its endeavour to effect "balance" at this right-hand end, exert an equal force at its junction with the left-hand piston's rod, from where it is transmitted, together with the left-hand piston's load, to the indicator, which now indicates the combined or collective load. Thus each piston's load is 100 lbs. by area of piston, whether this rod exists or not.

Mr. Henderson's ideas make the right-hand piston responsible for the whole load, and the left-hand one consequently has no load, which again do not agree with the experimental results, and consequently are wrong.

These experiments may be multiplied indefinitely; conducted with separate cylinders of the same, or different diameters; with

cylinders and pistons arranged as at Fig. 1 or Fig. 2, or any other way, provided the rod of each piston be arranged so that a load indicator may be attached to indicate each piston's individual effective load, with the one result, viz., that each individual piston's effective load will be that obtained by multiplying the difference of pressures acting on that piston at either side by area of that piston.

In arrangements of cylinders such as shown in Figs. 1 and 2, the rods may be arranged to work freely through one another. It is probable that had Mr. Henderson drawn his figures with such rods, we should never have heard of these mistaken views of his and Mr. Isherwood's. They are evidently an outcome of mistaken and unnecess ary uses of the term reaction, which has led them into the error of considering the cylindrical column of steam acting between the two pistons as a solid body, or more correctly, as a "perfectly rigid body" in direction of its axis.

Mr. Henderson's imagined discovery, respecting the reduction of back pressure in compound and triple-expansion engines, is perfectly wrong in consequence of being dependent on these ideas, which have been shown by experiment to be wrong.

If the principles of mechanics be admitted, it will suffice to disprove this article of Cassier's Magazine, to remember that as a force is specified by its magnitude, direction, and point of application, and two or more forces acting at a point in the same straight line may be replaced by their "resultant," by considering the junction of the piston rod with its piston as the point of application of the two forces, due to the steam repulsive effort at each side of the piston, which may be considered replaced by their resultant, which is in magnitude, their difference; and as no other force which here concerns us acts at this point, this resultant will completely represent this system. No forces acting at a distinct and distant point, such as at another piston, can influence this resultant, no matter whether it be equal in magnitude, opposite in direction, and in the same straight line, or otherwise; for it is not part of that system. Two such forces could only be considered together, and as rendering each other non-effective when taking the two pistons as "perfectly rigidly connected," and the two systems as one system.

In defiance of the above, Mr. Henderson would make out that forces acting at various points in the same straight line, which correctly may be considered one system and replaced by a single resultant, may be divided into as many minor systems as there are points, each of which minor systems may be replaced by single resultants which act at their respective points, but which represent component forces which act at distinctly different points, and hence belong to distinctly different (minor) systems, which is absurd,

d

S.S. "CANADA."

THE Royal Mail twin-screw steamer Canada, of which we have pleasure in giving two views, represents her in Alexandra dry dock, getting lower part of hull painted and receiving stores prior to sailing; the other at wharf outside, just before sailing. The vessel was built by Messrs. Harland & Wolff, Belfast. Full particulars of the launch we gave in our June issue. The dimensions of the vessel are, viz:-Length, 500 ft.; breadth, 58 ft. ; and depth, 31 ft. She has 6 cylinders, two 28 in. diameter, and two 471 in. diameter, and two 77 in. diameter, with a stroke of 54 in. She was taken out for her trial trip in Belfast Lough on Saturday, September 26th, and proceeded on her maiden voyage from Liverpool to Montreal on October 1st. Captain James M'Auley, of Ballymena, is in command.

IMPROVEMENT IN ELECTRIC CABLES FOR SHIPS.

ESSRS. W. T. GLOVER & Co., Salford, Man

chester, are bringing out a new and improved form of armour for electric cables, which has been specially designed with the object of overcoming the difficulties and disadvantages usually met with in cables having an earth or bare return, and as cables of this class are frequently used in ship lighting, a short description of this invention will be interesting to our readers. It is well-known that if ordinary iron or steel wire armour is used for the purpose of conveying energy, especially in cables of large size, the weight of metal required to accommodate the current is so great, viz., about seven times that of copper, that the cables

"true

e

It may not be out of place to here remind engineers, that the power diagram for any cylinder during either stroke, is not as given by the indicator with its pencil on the paper during that stroke, but as drawn below, where a, b, c is the steam line, and d, b, e the back pressure line for that same strcke; the dotted line diagram being the "true" power diagram for the cther stroke. In diagram a, b, c, d, e, the area a, b, e is positive, and the area c, b, d is negative; the similar areas on the other stroke diagram are similarly positive and negative. These negative areas largely influence the noise of the engine when running, and with inverted crank shaft engines, should be always largest on the down stroke diagram. The I.H.P. for both strokes collectively, is, of course, the same, whether calcalated from the "true," or what may be termed the apparent diagrams; but considered separately as for "balance," there may be great difference.

Santa Fe.-The torpedo-boat destroyer Santa Fe, lately built for the Argentine Government by Messrs. Yarrow & Co., has safely arrived at St. Vincent. She left Plymouth on Sunday, September 20th, and encountered the full force of the recent gale in the Bay of Biscay, which is one of the many illustrations of the sea.worthiness of this small class of vessel.

ARMOUR

are both costly and unwieldy. In Messrs. Glover's new arrangement, however, the cables are completely sheathed with iron or steel segments forming a conductivity-wedge armour, the round wires being of intersected copper, thus reducing its weight, and at the same time giving a complete steel armour, which is far superior to that of round wires. The surface of the conductivity-wedge armour being smooth and continuous enables the cable to be nicely finshed, whilst at the same time it is protected from accidents by picks, stones or sharp instruments, which might otherwise force their way through a round wire armour. It may be added that Messrs. Glover manufacture from the smallest to the largest sizes of cables required for ship-lighting purposes, the quality being guaranteed, and the length in which such cables can be supplied is practically unlimited.

and a back nut b, with a removable slide containing two small holes regulating the oil supply. Below is attached the combined retort, jointed by screws h and a projection containing two feeding holes leading the oil into the retort.

From the retort run the gas tubes G to the back burner for heating the retort. This burner has a removable cap H for cleaning purposes, and is attached to the cylinder end by a nut. The illuminating burner is situated within the retort. The cylindrical casing K is fitted at the back end with

I

FIG. 1.

FIG. 2.

view showing the lamp suspended upon a simple form of support. Referring to Figs. 1 and 2, it will be seen that the frame A, for suspending the apparatus, carries the petroleum reservoir B, which is fitted with a sieve. A pipe C from the reservoir has a petroleum valve D at its lower end. To the valve D is fitted a pipe E, with a union joint a and a removable sieve,

FIG. 3.

screws to secure the end cover, and underneath is arranged a spigot L, for use with tripod in place of the suspending hook. The windguard M is hinged to give access to the retort. Removable superheaters P1 P2 are provided to start the lamp with. The method of lighting the lamp is to first charge the reservoir B with ordinary lamp oil, first having closed the valve D; the windguard M is now opened and the two superheaters P1 P2, filled with cotton waste soaked with spirits are inserted, the small one being placed under the front burner and the larger one under the retort, and when in place they are lighted.

After the retort has been heated in this way about 10 minutes the valve D is opened, when a strong, sharp-pointed flame appears. The superheaters can now be removed, the flame adjusted, and the windguard closed. The lamp will now burn without attention until the reservoir requires replenishing with oil, which can be effected without stopping the light. From this description it will be seen that the light is generated by the automatic evaporation and superheating of ordinary lamp oil, which is conducted in drops into the retort. The back burner heats the retort, and by reason of its flame completely surrounding the front burner, the extinction of the light, even in the highest wind, is almost an impossibility. The high velocity of issuing flame from the burners causes an inductive action on the air which it draws in to the cylinders, so that it becomes warmed, and thus produces a smokeless dame.

We understand that a light of 3,500 candle-power can be produced by this lamp with an expenditure of 6 pints of oil per hour, costing 51d.

W

NAVAL MATTERS-PAST AND PRO-
SPECTIVE.

(From our own Correspondents at home and abroad.)

WEDNESDAY, October 21st, was the ninety-first anniversary of the battle of Trafalgar, which London especially, but, in. deed, the whole Empire, celebrated with extraordinary enthusiasm. The demonstration was in every way important and significant. It was a genuine and spontaneous celebration without a trace of official prompting, and must be regarded as another sign of that extraordinary revival of interest in the Navy which we believe will come to be regarded as one of the most remarkable developments of the close of the nineteenth century. The Navy League is another sign of this new growth of maritime ardour. It is to this body of civilians, inspired by the recessity of arousing the country to an intelligent interest in the Navy, that the initiation of the celebration of the lesson of Trafalgar is due. For it is to be remembered that this unexampled outburst of patriotic feeling was not merely a celebration of Trafalgar, nor a celebration of the memoy of Nelson. The battle was an event, the impor. tance of which can escape no intelligent person; the commander, a man of transcendent genius, a man of peerless valour and matchless seamanship; but the need which the League has realised is that, if this Empire is to last, it must be not by means of another Trafalgar, nor even by the aid of another Nelson, but by maintaining the sufficiency and pre-eminence of the Navy at a standard which will render unnecessary either battle or saviour. In the words of a great writer, "It is no mere stake of pride, power, or prestige that depends on the indisputable supremacy of our Navy. It is the very existence of the Kingdom and the Empire."

The Gunboat Flotilla on the Nile.

Now that active operations have ceased on the Nile, and Dongola is in the hands of the victors, it will not be out of place before the matter is forgotten to refer to the excellent service performed by the gunboat flotilla on the Nile. Three of the boats were engaged with the forts at Hafir, where Commander the Hon. Stanley Colville was slightly wounded. The loss on board the gunboats was not severe, but some extraordinary risks were run, for not only was a hot fusillade from rifles poured upon them at close quarters, but the guns of the enemy were well served. In one case a shell was lodged right in the magazine, and but for the fact that the fuse was not in it, the boat must have been blown up and sunk. The Tamia, Meternich, and Abu Klea were engaged in this affair, being commanded respectively by Commander Colville, R.N., Captain Oldfield, R.M.A., and Lieutenant Beatty, R.N. The fourth gunboat, under Commander Robertson, R.N., equally maintained the reputation of the Navy for dash, resourcefulness, and gallantry, but was delayed owing to a defect in the machinery. These boats were engineered by the contractors, and although we have not the

names of those in charge, that they one and all did their duty is clear from the reports of the correspondents at the front.

American Torpedo Boats.

The tiny torpedo boat flotilla of the United States Navy is growing apace. Messrs. Herreshoff have just launched one of the two they are building, and she is, pending the selection of an This beat, nominally appropriate name, to be known as No. 6.

of 26 knot speed, is expected to attain a speed of 27 knots. Her machinery is of simple design, and she differs from the Ericsson and Cushing in having her auxiliary engines disconnected from the main engines. Furthermore, experience having demonstrated the disadvantages of a tube placed directly in the bow, it has been decided not to supply the new boats with this tube, and it will probably, as in the case of some of the British boats, be removed from the Ericsson. If all the new boats are placed in hand the class will consist of twenty-one vessels, of which the three first are named the Cushing, Ericsson and Stiletto. Whether the other boats will receive names appears at present to have been undecided, but the department has suggested that in these vessels should be commemorated the naval worthies whose memories should be kept green. Among those suggested for such commemoration are Paul Jones, Preble, Farragut, Hull, Laurence and Porter. The circumstance, however, that the latelylaunched boat has not received a name, seems to indicate that this suggestion has not obtained official approbation. Contracts have been awarded for new boats to six firms. Two 30-knot boats are to be built by the Bath Ironworks, and one by the Union Ironworke. Two 224-knot boats will be built by Messrs. Wolff & Zwicher. Three 20-knot boats will be built by Messrs. Herreshoff, two by the Columbian Ironworks, and one by the Charles Hilman Co.

Naval Mishaps.

During the month of October intelligence of several serious accidents connected with the Navy were received at home. In two instances these mishaps were attended with serious loss of life. From the China station the Admiralty received a telegram reporting that on September 11th a boat belonging to the Narcissus capsized in Grossevitch Bay, and that Captain Lang, of the Narcissus, and three able seamen were drowned. Captain Lang, it appears, had landed with a shooting party in the Fish river, and it was when returning to the vessel that the accident occurred. The disaster was seen from the ship, and a cutter under the command of Lieutenant Gaunt put off to the assistance of their shipmates, and succeeded in saving Captain David Mercer, of the Marines, Mr. Dalrymple, midshipman, and three of the boat's crew. A somewhat similar mishap occurred on the Pacific station on September 6th, by which a lieutenant and seven seamen lost their lives. It seems that when at anchor in Unalaska Bay on that day, the galley of the Satellite left the ship in charge of Lieutenant Hayman, who had volunteered to bring off two men who were on shore, and unable to return in a small boat owing to the strength of the wind. The galley reached the shore safely, but in attempting to return was unable to make headway in face of the violent squalls. The lieutenant therefore decided to put before the wind and row for the beach. In doing this the boat was swamped, and only one man succeeded in getting ashore alive. During the boisterous weather several other mishaps were reported, but although some writers have attempted to draw from these occurrences the deduction that seamanship is diminishing in the Navy, those who are better informed declare that any such inference is entirely untrustworthy.

Launch of an Italian Warship.

The launch of the armoured cruiser Carlo Alberto, a sister ship to the Vetta Pisani, took place on September 23rd at Spezzia, in the presence of the King of Italy. This cruiser has a displacement of 6,500 tone, with 325 ft. length, 59 ft. beam, and 22 ft. 6 in. draught of water. An end-to-end belt of steel, supplied from the Terni establishment, gives the principal protection, but there is further plating in the battery, the maximum thickness of steel used being 6 in. The battery is casemated, the guns being separated by bulkheads, and closed in above with 2-in. steel, while the armoured deck below is 1-4 in. thick. The principal battery consists of twelve 5·9.in. quick-firers, of which eight are on the broadside, in the casemates already described, and four at the corners of the deck above. She carries aleo six 4.7-in., ten 2-2-in., and eight 1-4-in. quick.firere, with five torpedo tubes. The machinery, consisting of two triple