the other, or supposing the speed to be diminished on the gradient to 17 miles an hour, to but 50 horse-power. The carriage is not of the omnibus kind, but has 7 compartments, and guardsvan, in all respects in conformity with the standard rolling stock of the English lines. The weight being in no case greater than two and one-half tons per wheel, lines of corresponding lightness would serve as well as heavy lines now serve for heavy engines, loaded as they are from 5, 6, 7, and even 8 tons upon each driving-wheel. If even half filled with passengers, such a carriage at ordinary fares would earn about 5s. per mile, and if filled about twice as much. The whole cost of working would be small. When working upon moderately easy gradients, the consumption of coal would run but from 6 to 8 lbs. per mile, the wages of stoker, driver, and guard making 100 miles a day, to 1 d. per mile, including all train charges. Permanent way, station expenses, and general expenses might carry the whole to 1s., or 1s. 3d.; but even at twice the last-named cost, there would be a high proportion of profit on the work. The motion of the carriage is easier than that of an ordinary train; the total wheelbase being so much longer and yet so much easier from being formed upon swivelling bogies. It is almost impossible to imagine that if branch-line and other short traffic passengers were allowed to use this carriage, they would not universally pronounce in its favor. Mr. Fairlee, the designer, having worked out his system upon the great scale, and with the most perfect as the experiments at Hatcham have abundantly shown, is not only to be congratulated, but is entitled to the warmest thanks of the whole railway body politic.-Engineering.

success,

DURABILITY OF ENGLISH LOCOMOTIVES.

The life of a locomotive boiler has been found to be about 350,000 train miles; but this may probably on some lines go up to 400,000, or even 500,000 miles, as its wear and tear would depend greatly on local circumstances, and particularly on the chemical qualities of the water employed. Assuming that the life of the engine is determined by the endurance of the boiler, and that if, under favorable circumstances, it will last 500,000 miles, then during that time the fire-box will probably require to be renewed at least 3 times; the tires of the wheels, 5 or perhaps 6 times; the crank-axles, 3 or 4 times; and the tubes probably from 7 to 10 times.- Van Nostrand's Engineering Magazine, Sept., 1869.

PEAT FOR LOCOMOTIVE FUEL.

The State-Line Bavarian Railway has been worked with turf since 1847, or for above 20 years, rather from necessity than choice. The peat is got from the bogs of Haspelmoos. The method of its preparation is that of M. Exeter, whose statement is that he can produce 10,000 cubic metres of prepared turf per annum, at a cost of 2.80 francs per metre. The turf, as dug or

dredged, appears loaded with much admixed earthy matter; from this it is separated by grinding up, large dilution with water, and decantation of the water bearing the light peat particles still in suspension from the heavier earthy matter which has deposited. This is left to dry in layers exposed to the air like " hand-turf," and compressed in moulds by power. From other sources of information on the subject of artificially prepared peat, we conclude that these results admit of being contested. As a locomotive fuel, turf, at the best, is a bad and troublesome one; it gives much smoke and sparks, leaves an evil smell after it, experienced in the train, and is so bulky as often to need supplementary wagons to feed the tender on a long run. There is also great waste by the broken particles passing through the fire-bars. As to comparative heating powers (not theoretic, but taking into account all these circumstances), the result of 9 years' working on the Bavarian State Line indicate that 100 cubic feet, or 2.486 cubic metres, of the prepared turf of average quality and dryness, are equivalent to 312.5 kilograms of coke, or to 3.135 cubic metres of white firewood, that is, of wood principally of birch, beech, and alder. Thus, during this interval of working, the cost of firing with turf was about half that of coke in Bavaria, and two-thirds that of wood. By taking everything into account, as derived from the accounts of the line for 1861-62, it may be shown that even this is too favorable, for that the fuel account per kilometre per engines stands thus:

Passenger Engines,

-

Luggage Engines,

Fired with Peat. 0.172 f.

0.207 f.

It is thus, though rather cheaper than coal for slow traffic, a trifle dearer than coal for fast, and that even in Bavaria, where coal was then exceptionally dear. Van Nostrand's Eng. Mag., Oct., 1869.

BRIQUETTES.

The general use on the Continent of " Briquettes as fuel for locomotives is a matter of deep interest to our railway companies, both as respects economy of consumption and room required for storage. They are composed of finely powdered, washed coals, cemented with a material which forms the refuse of starch factories, or with coal tar. The mixture is subjected to the pressure of a piston in a cylindrical or polygonal case, and then exposed to a current of hot air in a kiln for about 3 hours. The resulting blocks weigh on an average 8 pounds, and burn with a residue of from 4 to 7 per cent. of ashes. The experience of the Austrian railways is, that they evaporate 7.2 pounds of water per pound of coal.

NAPHTHA AS FUEL FOR LOCOMOTIVE ENGINES.

M. Portski, a Russian engineer, has run a railway train successfully for a distance of 53.6 English miles, the only fuel applied

being raw commercial naphtha, instead of coal, coke, or wood. · Les Mondes.

AERO-STEAM ENGINES.

STORM'S EXPERIMENTS.

During a period of several years, dating from about 1851, Wm. Mount Storm, an inventor and engineer of considerable note, made a series of experiments with air and gases in connection with steam, with a view to promote economy in fuel used for generating motive power. An engine, called the "Cloud Engine," was exhibited by him at the Fair of the American Institute, in 1855. The engine was named as above from the fact that the air, which was mingled in the cylinder with the steam, changed the latter into a vesicular condition, resembling fog. The inventor claimed 33 per cent.; and those who saw it state that, at times, it did actually make a gain of even more than this.

Its operation was, however, fitful and unreliable, and it finally was withdrawn from public attention, and nothing more has been heard from it.

None of these experiments, however, seems to have been made on the same principles as those of Mr. George Warsop, of Nottingham, whose object is to attain to a method whereby the expansive force of heated air may be used in an engine without the difficulties attending the use of heated air alone in the cylinder, and which are met with in the engines of Ericsson, and others employing only heated airs.

In Warsop's experiments the object seems to have been to make steam assist in applying the expansive force of air.

Warsop, however, has found that a maximum effect from mixed air and steam depends upon the proper proportion of the two gaseous bodies, a conclusion which might have been theoretically drawn from a consideration of the relative capacities of air and steam for heat. Still such an inference would scarcely have warranted great hopes of economy from this source without extended experiment, and although extraordinary results-stated in a former article. —are claimed, we shall not be surprised to hear that some offset to these claims has ere long been discovered.

Incidental to the results sought by Warsop is of course a better circulation in the boiler employed to generate the steam used in the experiments, from which some gain might be expected, though nothing like what is claimed.

AERO-STEAM ENGINES.

To the mechanical engineer, the paper bearing the above title, read before the British Association, at Exeter, will be one of the most interesting of any of the able and valuable contributions to the transactions of that distinguished body.

The first part of the paper was devoted to a review of the data

by which it has been satisfactorily established that not more than one-tenth of the entire heat of coal is on the average utilized by steam engines.

The author, Mr. Richard Eaton, of Nottingham, England, then discusses the practical difficulties encountered in the effort to substitute heated air for steam, the principal of which is, as our readers are already aware, the effect of highly heated air upon such metals as may be economically employed in the construction of machines.

He then proceeds to give a brief history of the new aerosteam motor, which avails itself of air expansion, using at the same time steam, which removes the difficulty above mentioned.

In the first attempts at practically carrying out the system, the arrangement adopted was an ordinary high-pressure engine with vertical boiler as used where fuel is cheap. An air-pump is added, which is put in operation by the action of the steam engine.

Thus, cold air is taken in by the air-pump, and is forced on in its compressed state through an air-pipe, which, in the case before us, is conducted first within the exhaust, then in a coiled form down the funnel of the boiler, then past the fire, and finally past a self-acting clack-valve at the bottom of the boiler into the boiling water itself; rising naturally through the water, the air is intercepted and subdivided by diaphragms of metal gauge. Thus a twofold service is rendered by the contact of the elements, the water becoming aerified and deprived of its cohesion and prompted to a free ebullition, while the air on rising above the water is saturated by the steam, and the two together pass on to their duty in the cylinder where saturation assists lubrication. The agitation of the water prevents scaling.

In this form of the apparatus the power obtained by the increased volume of the air forced in by the pump did not compensate for that consumed in forcing it into the boiler. At the same time there were encouraging indications which led to further experiment. One of the air-pumps being discarded, experiments were made with waste-holes in the barrel of the other pump, to ascertain what proportion of air admitted to the boiler compensated for compression. It was found that about 10 per cent. of the effective consumption of fluid in the working cylinder gave much better results. At the same time the cam motions were discarded and the pumps left to their own unaided action. In this form it is claimed that a gain in work done by the combined air and steam engine was made of 42.5 per cent.

Here, although a very remarkable relative economy was apparent, it became obvious on consideration that danger of mistake would arise in assuming this economy as absolute, inasmuch as the duty performed, when contrasted with that obtained from engines of standard types, actuated by steam, was manifestly low, and it seemed probable that, as, by judicious improvement in details, the duty was made to approximate more closely to fair steam-engine duty, this relative economy might fall off considerably, inasmuch as there would be less margin to economize upon.

With a view of testing this point, and also for the satisfaction of railway engineers, of conducting experiments at locomotive pressures, a thorough remodelling of the whole apparatus was effected. The tappet motions were thrown aside in favor of the usual slide-valve arrangement, working with a moderate amount of expansive action. The former wasteful vertical boiler was discarded in favor of a more economical one of the compound or Cornish multi-tubular description, so as to obtain a better evaporative duty from the coal consumed. The radiating surfaces of the cylinder-pipes were reclothed, and the feed water heated by the exhaust steam. Instead of exposing the air-pipe to the direct heat of the furnace, as in the former case, the air became thoroughly heated on its passage from the pump to the boiler at a temperature of from 500° to 600° Fah., by being conducted through suitable coils and pipes through the exhaust steam in the heater, and the waste heat in the boiler flues and uptake.

When these changes were made a gain of 47 per cent. over. steam only, was claimed on an even-pressure trial, and a gain of nearly 30 per cent. on an open-valve trial, a step in advance so huge that it staggers belief.

AMMONIACAL GAS ENGINE. BY F. A. P. BARNARD, LL.D., COMMISSIONER TO THE LATE FRENCH EXPOSITION.

If hot-air engines and inflammable gas engines fail as yet to furnish power comparable to that which steam affords, without a very disproportionate increase of bulk, and for high powers fail to furnish it at all, the same objection will not hold in regard to the new motors now beginning to make their appearance, in which the motive power is derived from ammoniacal gas. The gas, which is an incidental and abundant product in certain manufactures, especially that of coal gas, and which makes its appearance in the destructive distillation of all animal substances, is found in commerce chiefly in the form of the aqueous solution. It is the most soluble in water of all known gases, being absorbed, at the temperature of freezing, to the extent of more than 1000 volumes of gas to one of water, and at the temperature of 50° F. of more than 800 to one. What is most remarkable in regard to this property is, that, at low temperatures, the solution is sensibly instantaneous. This may be strikingly illustrated by transferring a bell-glass filled with the gas to a vessel containing water, and managing the transfer so that the water may not come into contact with the gas until after the mouth of the bell is fully submerged. The water will enter the bell with a violent rush, precisely as into a vacuum, and if the gas be quite free from mixture with any other gas insoluble in water, the bell will inevitably be broken. The presence of a bubble of air may break the force of the shock and save the bell.

This gas cannot, of course, be collected over water. In the experiment just described, the bell is filled by means of a pneumatic trough containing mercury. It is transferred by passing