manner to produce, with equal leads, practically equal port-openings and cuts-off at each end of the stroke. In the diagram, the lines marked (1) show the middle and two extreme positions of the controlling lever; the lines marked (2) show various positions of the swinging link, by which the eccentric rod is suspended from the end of the controlling lever; the oval marked (3) being the path of the upper end of the eccentric rod; the lines marked (4) are different positions of the compensating link, and the lines (5) and (6) corresponding positions of the levers.

The shaded parts correspond to the port openings at the top and bottom of the cylinder and indicate the practical equality of these openings.

If we calculate the nominal horse-power of these engines at 30 circular inches we find them to be 164 N.H.P.

The I.H.P. is, therefore, when working at this reduced pressure, 5.29 times the N.H.P., and is pretty equally divided between the three cylinders; this is even more apparent when working at full pressure.

1.5 lb. per I.H.P. per hour. The consumption is stated by the builders not to exceed

Steam is generated in two single-ended steel boilers 13 ft. 6 in. diameter and 9 ft. 6 in. long.

Each boiler has two of Fox's patent corrugated furnaces 6 ft. long and 3 ft. 7 in. mean diameter.

All the joints of this gear is fitted with simple and convenient brass bushes and bolts, so that they are easily adjusted. The valve spindle ends resemble the piston rod crosshead, having slipper, guides which work on motion bars on the back of the columns; the brass bushes, however, slide a little to suit the motion of the oblique lever.

Fig. 3 is a set of indicator cards compared with the theoretical card. It will be noticed that the initial pressure in the H.P. cylinder comes very near the boiler pressure, and also that there is practically no loss between the H.P. and I.P., and between the I.P. and L.P. respectively.

The firegrate is 5 ft. 9 in. long, and each furnace has a separate combustion chamber.

The working pressure is 150 lbs., and the boilers are tested to 300 lbs. per square inch by hydraulic pressure. Pipes and valves are provided for pumping the water from the bottom of the boilers, and delivering it in again at the water level by the ordinary feed donkey, and so perfectly circulating the water in the boilers while raising steam; this is also intended to be used at sea to guarantee the removal of stagnant water from the bottom of the boilers, but difficulty is sometimes experienced in getting the donkey to pump when under full pressure. While raising steam, however, it is found that with this arrange

ment the boilers warm very evenly. The longitudinal seams have double-butt straps and three rows of rivets on each side of the butt. Machine riveting is applied as far as possible. The shell plates are flanged to meet the end plates and are welded at the corners. The seams round the furnace mouths are turned outwards and so kept clear of the fires.

Each furnace has two small doors, so that the fires can be spread very evenly, and the clinker removed with. only one door open at a time; but the principal object of the two doors is to keep the fires always bright by firing at alternate sides, allowing one side to burn through before firing the other. These boilers are found to generate a sufficient supply of steam without being pressed, or the fires much worked.

A steam-reducing valve is provided for supplying steam from the main boilers to the winches and steering-gear. We have endeavoured throughout this article to give a correct account of these engines; to confine ourselves, as far as possible, to a description of the engines and boilers as they are at present produced by the firm named, noticing principally those points where makers differ, and where recent improvements have been introduced, and we hope to have the pleasure of giving similar accounts of the Triple Expansion Engines of other north-country engineers, which we have no doubt will be interesting to readers at the present time, when this type of engine is coming so prominently forward.

HIS well-known firm, of £5, Queen Victoria-street, E.C., have a very good display of machine tools at their stall (No. 1,216) in the Western Annexe. Amongst the tools we noticed is the patent Self-acting Band Saw Filing Machine, which we fully described and illustrated in our issue of January last. This handy tool, which propels the saw and sharpens it at the same time, is shown in motion. Another machine, which could not but prove useful in the engine room, is a Treadle Planing Machine, yclept the "Eureka." The machine can be fitted to run either by hand, treadle, or power, and is made in three sizes, the smallest to plane 22 in. long, 13 in. wide, and 8 in. high, while the largest takes 40 in. by 18 in. by 16 in. The "Eureka" works continuously in one direction, is fitted with reversing motion, and has a practical disengaging motion which admits of the work being stopped instantly, even when reversing. Another tool, shown here for the first time, is a patent Screw Lathe, fitted with clutch, back gear, chasing apparatus, self-acting feed for milling, and longitudinal feed for the cut-off rest. The lathe is made in two sizes capable of turning out screws from 1 in. to 12 in. diameter, and from 1 in. to 2 in. diameter respectively. The special features of this tool are a self-acting revolving turret, and an automatic feed with an adjustable automatic stop.

PORTABLE TIDE-RECORDING MACHINE.

As much attention now is paid to accurate scientific observations of the rise and fall of tides, or the rise and fall of water in wells, or to the depth of water falling over gauge weirs, to guide engineers in their professional work depending upon these subjects, any instrument promising special accuracy in the register of these subjects merits attention. The tide-recording machine we are about to describe is the invention of Mr. Baldwin Latham, and consists of a drum which is driven once round in twentyfour hours, with a suitable clock arrangement to indicate the time. As pendulum clocks are not reliable for work on wooden piers subject to vibration, the clock in this case is controlled by a balance wheel and lever escapement. The level of the water is indicated by a float, the float being attached to a wire cord, which is securely fixed to the drum. The float, in its descent, acts upon a spring winding it up, so that as the float rises the spring again picks up the slack cord. In order to render the strain of the spring uniform, the well-known fuzee arrangement is introduced between the spring and the float. The drum, operated by a movement of the float, carries a pinion which actuates a marking pencil by a rack. There are four different-size pinions provided with the machine, so as to produce diagrams to four different scales, as desired. The pencils for recording are arranged by a parallel motion, so that as the pencil point wears away the pencil is pressed forward without any alteration of its correct position on the diagram.

The drum travels upon a screwed spindle, so that the cord shall always pass on and off in a perpendicular line: this prevents error from the lengthening and shortening of the cord, which would ensue were the drum a fixture and the cord spindle drawn off the drum on varying angles. The apparatus is thus very simple, portable, and self-containing, so that it can be easily fixed in a few minutes in any position in which it is required to work. This instrument has already been used in a very large number of tidal observations by the inventor on behalf of the Corporation of the City of London, so that its merits have been well proved. The machines are manufactured by Mr. Joshua Richmond, of Church-road, Islington, who exhibits a sample of the machine in the International Inventions Exhibition, the workmanship and finish of the machine being very creditable to the

maker.

MODELS OF SHIPS AND ENGINES AT THE INTERNATIONAL INVENTIONS EXHIBITION. PERHAPS no more conclusive evidence of the gigantic strides made during comparatively recent years in the kindred sciences of naval architecture and marine engineering, could be obtained than is furnished by a

careful inspection of the various models, sections, and photographs shown in Group VII. at the Inventions Exhibition, commencing with the exhibit made by the Lords Commissioners of the Admiralty at No. 921, we find models of the following of Her Majesty's ships: Inflexible, Devastation, Monarch, Rupert, Glatton, Opal, and Staunch. We must candidly confess to a feeling of deep disappoinment at the meagreness of this display, considering that it is made by those whom are supposed to represent the naval supremacy of the world.

The Barrow Shipbuilding Company, Limited, of Barrow-in-Furness, exhibit at Stand No. 928, some very fine half models of ships.

Messrs. Laird Brothers, of Birkenhead, No. 930, have a collection of models and photographs, which from an historical point of view, possess especial interest, illustrating as they do the progress made in paddle、 wheel Channel mail steamers since 1840, and in screw

the Nile expedition, and the model of four sea-going torpedo-boats built for the Brazilian Government.

Messrs. Oswald, Mordaunt & Co. have a very good display, at No. 947, of models of steamers, and several special models illustrative of improvements introduced by them.

The most perfect model of marine engines, and we believe the only one in motion, is that exhibited by Messrs. Maudslay, Sons & Field, in Group IV. (No. 407). It is a model of the four-cylinder compound engines as made for vessels of the White Star Line, and the Cie. Genéralé Transatlantique of France.

NOTES ON SHIPBUILDING.*

By Mr. J. H. BILES (of Messrs. J. & G. Thomson), Clydebank, Glasgow. me, as one

HEN the secretary of this Institution asked

"

graphs of early iron steamers.

One of these photographs shows a paddle-steamer, high and dry, in such a position as would, we think, terribly alarm some of our modern naval architects.

Sir W. G. Armstrong, Mitchell & Co., Limited, have at the next stand (No. 931) the finest and most numerous exhibit in this group, comprising as it does upwards of 40 models representing vessels from 90 tons displacement (steel paddle steamer Oput) to 9,000 tons displacement (twin screw cable steamer Faraday). It may be interesting to here mention, as showing the rapidity with which work can now be executed, that this Firm launched the cable steamer Silvertown, of about the same tonnage as the Faraday, in the extraordinary short space of 100 working days from the time the keel was laid, and entirely finished her in seven months from the date of order. They also exhibit a photograph and full model of a floating dock, built in 1877, for the Dutch Government service.

The White Star Line, exhibit, at 932, one of the best finished and most complete models that we have ever had the pleasure of examining. It represents one of their famous Atlantic passenger steamers, well named "floating palaces," and shows in a marked degree the amount of attention that has been paid to everything likely to conduce to the safety and comfort of the Atlantic passenger.

The Thames Ironworks and Shipbuilding Company, Limited, have also a very interesting display at No. 933, two of their models, representing the Warrior and the Benbow, show ironclads of the earliest and latest types, and if a general appearance of bulkiness is any criterion as to fighting qualities, then we should say that the latter vessel must be a great and welcome addition to our navy.

The Royal National Lifeboat Institution show, at No. 937, models of their improved self-righting lifeboats.

Messrs. Samuda Brothers, of Poplar, have very fine models at Stand No. 940, of the celebrated Riachuelo, armour-clad turret ship, and the Mary Beatrice steel paddle-wheel passenger steamer, built for the South Eastern Railway Company's service between Folkestone and Boulogne.

Messrs. R. & H. Green, of Blackwall Yard, E., occupy their space, No. 944, with a very well made model of a light ship.

Messrs. Yarrow & Co. exhibit, at No. 945, models of the stern-wheel steamers Lotus and Water Lilly, built for

"Steel Shipbuilding," I could not but feel honoured. The year that this Institution holds its meeting in the home of steel ship

building is not one when no contribution should be made to the

literature of this subject unless there is absolutely nothing new to talk about, and I therefore, though reluctantly, have prepared a paper which, I hope, will serve to elicit a valuable discussion, if it does not by itself impart any information.

There are two questions to be considered in undertaking to build any ship; the first is the constructive possibility, the second is the commercial desirability. The first has become a certainty, as is evidenced by the increasing percentage of the total ships built which are steel, and by the confidence which is now felt by the great majority who have had the necessary enterprise to build in steel.

The second has been several times demonstrated. First, by Mr. Martell, in 1878, who showed that a better profit could be made in a steel than in an iron ship; secondly, by Mr. William Denny, in 1881, before this Institution, who showed the price per ton of steel, in relation to iron, which must rule in order that, per ton of dead-weight carried, a steel ship should be as cheap as an iron one. Mr. William John, before this Institution last year, pointed out that the relation between steel and iron necessary to make a steel ship as cheap in first cost, per ton of dead-weight carried, had been reached. This was a great point for steel to reach, because it made a comparison of profits independent of the freights, which was not the case in Mr. Martell's comparison. I shall endeavour to show later on that we have reached, on the Clyde, a relative price of steel to iron, where for the same size of ship the cost is practically equal, and therefore the shipowner is in a position to have a considerable increase to his weight-carrying for the mere deciding whether his vessel shall be built of steel or iron. Why another iron cargo-carrying ship should be built upon the Clyde it is difficult to see; and I shall endeavour to show later on that even in ships where dead-weight carrying is not the desideratum, but where capacity is, by properly modifying the dimensions the full advantage gained by the dead-weight carrier can also be obtained by the measurement goods carrier.

With the change from iron to steel as a 'common material of ship construction, there must necessarily follow some changes, great or small, in the construction of the ship, and in the general design in so far as the weight and strength of the structureforming material affects the question of weight-carrying, stability, and principal dimensions. The experience of the last ten years in the manufacture of steel, and its application, among many other purposes, to ship construction, had enabled its users to say with certainty that a steel ship can be constructed with at least at much certainty of success in all respects as an iron, provided thas the dimensions are chosen, the structure is designed, and the work of building is carried out with a full appreciation of the fact that the ship is to be a steel one and not an iron one.

With the adoption of the 20 per cent. reduction allowed by Lloyd's, and as carried out in their latest volume of rules by the substitution of the same number of twentieths of an inch in thickness in a steel ship for the corresponding number of sixteenths in an iron ship, the reduction in the weight of material, after allowance has been made for the different specific gravitie of the two metals, must be about 17 per cent. But there are

Paper read before the Iron and Steel Institute, at Glasgow.