a pair of outside cylinders side by side, and connecting them to a crank and return crank, opposed to each other, on each side of the engine; so that the two pistons on each side, and all their connexions, move in contrary directions, and balance each other's inertia.

There can be no question that this system is perfectly successful in effecting the object in view; and had it been brought out twenty years ago, it would no doubt have been highly appreciated. But as the balancing of engines with two cylinders has, for the last ten years, been completely accomplished for all practical purposes, by means of counterweights, the use of four cylinders, as in this engine, is not likely now to become popular; unless, indeed, railway companies, in the race of competition, should aim at excessive speeds of 80 or 100 miles an hour.

The Austrian State Railway also exhibited the "Steierdorf," a heavy tank engine, with five coupled axles. The boiler rests on two frames, coupled together by a pivot bolt. The steam cylinders are fixed on the front frame, and the tank on the hind frame; and the three pairs of wheels of the front frame are coupled to the two pairs of the hind frame by means of an intermediate shaft and radiating parallel motion. This intermediate shaft is ingeniously contrived to adapt itself to the varying angularity of the hind frame, on curves, and at the same time to continue to transmit the power from the first to the second frame.

In the Prussian department, one engine was exhibited by Mr. A Borsig, of Berlin. It was a six-wheel four-coupled engine, with outside cylinders 17 inches diameter, by 22 inches stroke, and driving wheels of 4 feet 6 inches diameter, the hind wheels being coupled, and all the axles being between the fire-box and smoke-box. This type of engine is exclusively employed on the Minden and Cologne Railway for mixed and goods trains; and also on many other German railways. The free use of steel in the construction of this engine confers on it an air of lightness, perhaps too great lightness, which contrasts strongly with the heaviness of the tender.

The proportions of the boiler are good; and this circumstance, in addition to the very excellent and well-finished work, may account for the popularity of that class of engine.

In the Saxon department, a six-wheel four-coupled engine was exhibited by Mr. R. Hartmann, of Chemnitz, especially designed to work in mountainous districts. It is, in fact, a bogie engine, having four coupled wheels, 4 feet 6 inches diameter, with 21 tons on them for adhesion, and a swivelling truck, on Bissell's plan, in front, with 7 tons load, making a total of 28 tons. The cylinders are 15 inches diameter, by 22 inches stroke; and are outside, with outside valve gearing, as is so prevalent a custom on the continent. The framing has two longitudinal plates 8 inches deep, and 13 inch thick, to which the cylinders are fixed, with 16 inches of overhang. This is an excessive overhang upon so narrow a frame plate, and the valve gear being still further overhung, the valve hops about at every stroke as the axle-boxes wear. Overhung excentrics for valve gear outside the crank pin, never do well for heavy work, in consequence of the unsteadiness. The best feature in this engine is the swivelling truck, with a triangular frame, which carries the fore part of the engine on one pair of wheels, with a limited, but

sufficient allowance of lateral play, and radiates on a pivot behind it, fixed under the boiler. With a flexible wheel base, only 11 feet 9 inches long, there is no doubt that in this engine, and in others of ordinary size, the Bissell truck is well adapted for leading round the quickest curves likely to be found in practice.

In the Italian department an inside cylinder six-wheel-coupled locomotive is exhibited, from the Pietrarsa Royal Works, Naples, which is a creditable specimen of the old school of locomotive.

General Conclusions.-It appears that the requirements of continental railway traffic have demanded a greater variety of locomotive engines than has been found necessary in this country. Trains there are heavier; speeds are lower; and, more important than all, inclines are steeper. Whilst, therefore, the marks of progress in English engines are to be found mainly in refinements upon the original types, Foreign engineers have discarded our traditionary types, and have originated novelties in every direction. In England, engineers have arrived at higher speeds, with more powerful boilers, and increased driving or adhesion weight.

The means of satisfactorily balancing the reciprocating and revolving machinery, the want of which was previously the bane of the outside cylinder engine, by counterweighting the wheels and steadying the engine, have been discovered and carried into practice since 1851; so that the outside cylinder engine, properly balanced, now runs even more steadily than the inside cylinder engine. Outside cylinders have consequently been employed for high speed and other duty, with complete success: they have not, however, been employed for the heaviest work. The inside cylinder is generally retained for six-wheel-coupled goods engines, and is not likely to give way to the outside cylinder for that class of work, on account of the objectionable construction involved by outside connecting rods, combined with outside coupling rods for all the wheels. But for passenger traffic, with four coupled wheels, and the lighter traffic of collieries and other private establishments, the outside cylinder is well suited, and is extensively applied. It is, however, to be explained, that the advantage of the six-wheel-coupled engine is limited to the old and the comparatively straight lines of railway, on which the destruction of cranked axles is not rapid, and the wear and tear of tyres not severe. For lines with the prevailing sharper curves, the four-wheel-coupled outside cylinder engine surpasses, in efficiency and economy, the six-wheel-coupled engine, running on curves with greater facility, utilising the adhesion weight better, and being subject to less wear. Hence the six-wheel-coupled engine with inside cylinders, is to be found chiefly on the older and straighter lines. On the contrary, the outside cylinders, and the single and four-coupled driving wheels are to be found generally on the newer lines that have many quick curves.

In England the use of more than six coupled wheels in one engine has been avoided: three wheels coupled in one line are found sufficiently powerful and sufficiently troublesome, and it is preferred to supplement the power, when necessary, with an additional engine. On the continent, however, great efforts have been made to construct an efficient engine with great tractive force, and enormous weight for adhesion, to ascend long and heavy inclines peculiar to mountainous

districts. The subdivision and disposition of the weight in moderate loads on the rails has been effected with ease, by distributing it over a sufficient number of wheels and axles. But the most important part of the problem has been to reconcile the unavoidable extension of wheel base in a straight line with the excessive curvature of the railways; for naturally, though unfortunately, heavy gradients and quick curves are generally to be found in company.

The system adopted on the Northern Railway of France, in the "Dromadaire," must fail to answer these requirements; for with a wheel base so extended, the resistance of the engine itself must absorb a great proportion of the tractive power. A flexible wheel base is indispensable, and two ordinary engines, connected together, would work much more efficiently and economically than the vast masses actually employed. The opinion on the Northern Railway of France against the use of coupling rods in passenger engines, and the consequent substitution of two independent pairs of driving wheels, with independent cylinders, must appear to be erroneous. The truth is, that, for working four driving wheels, one pair of cylinders, with coupling rods, is the best method of providing adhesion weight; more especially since, by the use of steel for the tyres, their excessive and unequal wear, and the consequent straining of the coupling rods, are, to a great extent, prevented at all events, the wear of the tyres may be regulated and equalised, which removes the only objection worth consideration.

:

The Austrian plan of coupling over an extensive wheel base by a self-acting radial adjustment in the "Steierdorf," is decidedly a better plan, and merits a thorough trial. There is nevertheless a complication of mechanism with many rubbing surfaces, liable to occasional overstraining, from irregular play of the bearings arising in wear in transmitting the power over a long distance through a flexible connexion; and engineers have to look in another direction for a comprehensive and satisfactory solution of the problem.

The plan of Meyer's engine appears, in the writer's opinion, to be the best yet brought forward for distributing steam power over a flexible train of coupled wheels. It is based on sound principles, as experience will no doubt prove. It is known that, practically, a locomotive boiler, with ordinary management, delivers a better supply of steam to a given pair of cylinders fully worked at a low speed of piston than at a high speed: the steam blows off from the boiler, and there is plenty to spare. By making the boiler a little larger, therefore, it is justly reckoned that steam can be supplied for four cylinders at a low speed, as well as for two; and the train of wheels is therefore divided into two independent groups under the boiler, each group free to adapt itself to the line of rails, and fitted with its own pair of cylinders and the necessary coupling rods, and receiving a separate supply of steam from the boiler. In short, two steam bogies are employed, which carry the boiler and its accessaries just as a load of timber is carried on a couple of swivelling trucks.

The abstract importance of heating surface appears to have been overrated, particularly by foreign engineers; and the primary importance of free passage for the currents of water in intimate contact with the heating surface, whether of the fire-box or of the tubes, has been neglected. The width of the water spaces around the fire-box has

frequently been reduced to a minimum barely sufficient to preserve the plates from being overheated. The tubes have also been placed so near to one another, and in such large numbers, as totally to defeat their object of increasing the steam-producing power of the boiler, because they have rendered it impossible for the water, crowded with globules of steam, to reach the surface of each tube and become evaporated. Tube surface, under such circumstances, is ineffective, and ultimately becomes mischievous; for the sediment deposited by water in boilers. will, if not scoured out, coat the tubes and block up the spaces between them altogether. The greatest number of tubes known to have been applied in England is the 305 tubes of the Great Western express engine exhibited in 1851. In this engine, the tubes, 2 inches in diameter, are placed only 50 inch apart, and are not so effective for evaporation as the tubes of some of the earlier engines on that line, which were fewer in number, but placed at from 62 to 1.00 inch clear distance apart. In the English engines exhibited in 1862 the greatest number of tubes was 215 in Messrs. Beyer, Peacock, & Co.'s engine for the Portuguese gauge, with 56 inch clearance; and 214 tubes in the North Western inside cylinder engine with 50 inch clearance.

The best English practice exhibited in reference to the tubes is, in the writer's opinion, to be found in the North Western outside cylinder engine, the "Caledonian," and the Great Eastern engines, all of which, singularly enough, have identically the same proportions,-192 tubes, of 13 inch diameter, with 62-inch clearance, placed in a barrel 3 feet 10 inches inside diameter. The excellence of these proportions is confirmed by the very satisfactory performances of the engines under very different circumstances.

The greatest number of tubes exhibited in the foreign engines is 356 tubes with 44-inch clearance, in the "Dromadaire" class of engines on the Northern Railway of France, with the 4-ft. 8-ins. gauge. The drawings of the twelve-wheeled four-cylinder goods engines employed on the same railway show 464 tubes with 56-inch clearance but these proportions will undoubtedly disappoint the expectations of the projectors, and the experience of a few years will, it is presumed, correct these abstract ideas.

The distinction between fire-boxes for burning coal, and those for burning coal slack, should not be overlooked. For coal, 13 to 15 square feet of grate is sufficient; but for slack, the North Western inside cylinder engine has 26 square feet of grate, and the Chatham and Dover engine 27 square feet. The difference of fuel leads to a difference of treatment, inasmuch as special provision is made for the admission of air above the fuel, for burning coal in pieces, in addition to the air that passes through the grate. For coal-slack no such provision is made; the layer of fresh fuel is thin, and a sufficient quantity of air is drawn through the large surface of grate. At the same time, the slack is supplied in small quantities, and much more fre quently than coal in pieces.

In placing the machinery on the frame, it must be remarked that the foreign engineers seem to have merely shown how an inferior arrangement can be made to do. Next to excessive amount of heating surface their partiality is remarkable for overhung valve gearing upon outside

cylinders, which is undoubtedly the worst possible position for efficiency and handiness of the engines.

Giffard's injectors have been extensively employed as a substitute for the ordinary feed pumps; and their general adoption in locomotive engines, both in England and on the continent, is an evidence of their popularity and general efficiency. The only apparent objection to the use of the injector, is its inability to deliver heated water at a temperature of more than 120° Fahr.; this prevents the use of means for heating the feed water by the contact or mixture of the water with the exhaust steam; but the injector may be used with surface heaters, in which the water, whilst on its way to the boiler, may be heated after it has passed through the injector, by contact with steam-heated surfaces.

MANCHESTER LITERARY AND PHILOSOPHICAL

SOCIETY.

At a meeting of this society, held November 17th, 1863, E. W. BINNEY, F.R.S., F.G.S., President, in the chair, the following paper was read, "On a new method of producing carbonic oxide," by Dr. F. CRACE CALVERT, F.R.S.

IN 1820, my learned master, M. Chevreul, published a most interesting paper on various coloring matters, and drew the attention of the scientific world at that time to the property which most coloring matters possessed, of absorbing oxygen under the influence of alkalies ; and although he demonstrated the great advantage possessed by gallic and pyrogallic acids, as agents for analysing the atmosphere, by the extraordinary rapidity with which they absorbed oxygen under the influence of alkalies, still this valuable observation of M. Chevreul remained dormant for nearly twenty years, when Liebig again proved with what facility air could be analysed by this method. I wish now to call your special attention to this mode of absorbing oxygen in a gas mixture, as it is considered by many chemists to be quite as accurate as those methods which are based upon the employment of-phosphorus, or metallic copper, as suggested by Gay-Lussac; but this is not correct, for I have observed that it contains a serious source of error, because, during the absorption of oxygen by the gallic or pyrogallic acid, under the influence of alkalies, a certain quantity of a permanent and combustible gas is produced, viz.,-oxide of carbon.

It was during a series of experiments which I had undertaken, to verify a most interesting fact, published by M. Boussingault-viz., the production of oxide of carbon during vegetation under water, or the decomposition of carbonic acid under the influence of solar rays (see Comptes Rendus, vol. 63, p. 862, 1862),—that I discovered that the oxide of carbon, which M. Boussingault had obtained in his analysis of the gas mixture produced during vegetation, was not due, as he thinks, to the reduction of carbonic acid into oxide of carbon; but that this gas was a product of oxidation, or the result of the action of oxygen on the pyrogallic acid that he used for analysing his gas mixtures.