of the lower part of the water partition guard and the surface of the coke on the bars of the smoke-consuming chamber, is so adjusted, that the smoke, before it can find egress into the flues, must pass over the surface of the coke. The construction, thus explained, will make the mode of operation easily understood. The furnace is fed in the ordinary manner; each successive quantity of coal is deposited in the anterior part of the coal-chamber, and, as the furnace in succession requires feeding, the fireman forces back the fuel in the chamber till he has sufficient room for the new feed, the fuel in the posterior part of the coal-chamber being, by this process, projected into the smokeconsuming chamber. Thus, the latter chamber is entirely supplied with fuel in the highest state of ignition, emitting only a pure flame. Then the smoke arising from each successive feed in the chamber, having, from the relative position of the water partition guard, and the surface of the highly-ignited fuel in the smoke-consuming chamber, to pass under the former and immediately over the surface of the latter, is thus exposed to the intense action of the flame, and before reaching the flues is consumed. The boiler is in active operation on the premises of Mr. C. Smith, flax-spinner, Dudhope.-Dundee Chron.

BEST FORM FOR STEAM-VESSELS.

THE United Service Journal contains some interesting papers, by Lieut. Wall, R.N., "On the Construction, Proportion, and Power, best adapted to Sea-going Steam-vessels." In his last communication, he gives the following as the result of a careful examination of the experiments of Col. Beaufoy, Sir John Robison, and others:

1. That the resistance of a body passing through a fluid is as the square of the velocity.

2. That an increased facility in passing through a fluid is imparted to a body by an increase of its length.

3. The resistances of small superficies are nearly as the surfaces; but the resistance is greater than a proportional increase of surface, and this deviation from theory increases with the extent of surface. 4. The resistance to the passage of bodies through the water is proportional to the angle at the head, other r proportions being alike.

5. The resistances do not vary in the duplicate ratio of the angle of incidence.

6. For the higher rate of velocities, the flatter a vessel is built in the floor, the better, when intended to be propelled by machinery.

From which we infer: 1, that as double power will not propel the same body at double the speed, the larger steam-vessels are built, the better: 2, that the length of a vessel in proportion to her breadth may be increased beneficially, (for speed,) until the lateral resistance shall equal the increased momentum obtained by additional breadth, (which is at about eight times the breadth); that the extreme breadth ought to be exactly amidships; that the form of the bottom, below the waterline, ought to be as flat as possible for about three-fifths of the length, and from thence to draw in forward and aft for the entrance and run; and the bow to be as sharp as consistent with safety in a sea-way, but the run not to be too fine.

It is also recommended that the counters and harpings be kept full, the stern-post nearly upright, and the stern formed on the circular construction. In consequence of the shallowness of the vessel, the quarter-deck and forecastle should be covered in, by which much room will be obtained below; and the deck of the latter, being bevelled and carried well aft, will serve to turn any sea which may be shipped in steaming head-to-wind. The bulk-head of the quarter-deck cabin should be of a semicircular form, having ports cut at its junction with the vessel's side, for the escape of the wind.

Lieut. Wall also proposes to build large steamers with three instead of two engines; and sets forth advantages which would more than counterbalance the increased expense, weight, and friction of the third cylinder.-Quoted in the Mechanics' Magazine.

PROPORTION OF POWER TO ΤΟΝΝAGE OF STEAM-VESSELS.

MR. SCOTT RUSSELL has read to the British Association an important paper upon this subject of anxious inquiry with every proprietor and constructor of Steam-vessels. If, on the one hand, a large cargo is desired, which is generally the case, the power of the engine is made small, for the purpose of occupying small bulk, and consuming little coal; and although less velocity is then acquired than with greater power, still less fuel is consumed with a small engine than a large one, and thus it is supposed that greater economy is effected. In other cases, where velocity is absolutely required, a much larger proportion of power has been employed; and, of course, by a large power there is a much greater consumption of fuel than a small one in a given time; and not only so, but it is well known that this additional consumption is much greater than in the proportion of the velocity gained; so much so, that a consumption of four times as much fuel will not give more than about double the velocity. Thus, it has appeared that the use of very great powers, and great expenditure of fuel, has been made with only a very slight increase of velocity. All this, the usual reasoning on the subject, goes to prove the value of employing a small proportion of power to tonnage for economy. The advantage of low powers and of low velocities, in point of economy, would thus appear to be established: but this apparent advantage in theory has not been realized; on the contrary, it may be recollected, that at the Bristol meeting of the Association, Dr. Lardner remarked, that in a case which had come under his own knowledge, where the power had become gradually increased in the same vessel, and it was found that while the vessel was increased in speed, the consumption of fuel on the whole had diminished. This was a fact which Dr. Lardner attributed to Mr. Russell's Wave principle. Mr. Russell had himself attributed it at that time to the same cause; but he found afterwards, by examining the books of the expenditure of fuel in the steam-vessels of several companies, that they were aware that they had, on the whole, saved money by using high powers of steam, and high velocities, instead of low ones. This result he would not in the circumstances attribute to his Wave principle; and he had arrived at this very remarkable general result:-That in a voyage by a steam-vessel in the open sea, exposed, of course, to adverse winds, there is a certain high velocity and high portion of power, which may be accomplished with less expenditure of fuel and of room, than at a lower speed with less power. This principle he then proceeded to prove, and to illustrate by a case, in which the same vessel is taken with different powers of engine, and the result, as regards expenditure of fuel, determined first arithmetically, and then by a general formula, which will enable any one to determine any particular case.

Dr. Lardner remarked that the theory of Mr. Russell was quite new to him; but that he was satisfied of its accuracy. Mr. Russell added an important circumstance, in which great advantage might be derived from the application of high powers: thus, the owner of a vessel, which usually accomplishes her voyage in fifteen days, but owing to storms or adverse winds, occasionally takes twenty, must SO regulate her stated periods of departure as to allow for these adverse circumstances; and four or five such vessels may be required to keep up a regular communication between places for which three or four would be sufficient, if, by increased power, the average voyage were reduced to ten, and the adverse to fourteen, days; and thus, a large capital would be saved, as well as more voyages accomplished. This principle is, however, only applicable to vessels making long voyages.-Athenæum ; abridged.

AMERICAN STEAM NAVIGATION.

THE secretary of the navy at Washington has issued an interesting document of statistics on this subject, from which we may gather material for settling a question about the comparative Steam-boat force of England and America. In 1836, we had 600 steamers at home and abroad. Doubtless, the number has increased since then. The American number is rated at 800 now, of which 600 belong to the western waters, where, in 1834, there were but 254. About 140 belong to the state of New York. In tonnage, America is more in advance; the total there being estimated at 155,000, to about 68,000 on our side, two years ago, at the same time. The American boats do not equal ours in size: the largest runs between New York and Natchez, and is of 860 tons; the next in size are on Lake Erie, and along the New England coast. The average is 200 tons.--Athenæum.

STEAM-BOAT NIGHT SIGNALS.

THE Society of Arts have awarded to Mr. Jennings a silver medal for his invention of Night Signals for Steamers, to indicate to the steersman in what direction to vary the helm. The plan consists of three differently coloured lamps, fixed on a horizontal rod attached to a swivel, which the man on the paddle-box varies in position relative to the steersman's eye, and thus conveys to him the requisite orders.

STEAM-BOAT ACCIDENTS.

THE following interesting and important tabular results are selected from the Report of Captain Pringle, and Mr. Josiah Parkes, C. E., appointed by Government to investigate the causes and means of prevention of Steam-boat Accidents.

Particulars of Explosions, and form of Boilers.

It thus appears that 7 explosions have occurred in cylindric boilers.

15 ditto

Total.... 23

rectangular boilers.

1 ditto, the Eagle-form of boiler not ascertained.

19 Explosions happened whilst the vessels were stopping, or on the instant

3

1

of setting the engines in motion.

Ditto, whilst steaming.

Ditto, the Antelope, not ascertained.

23

ANTHRACITE IN STEAMERS.

MR. PLAYER has invented a Fire-place which is exactly suited to the peculiarities of Anthracite; enabling it to become slowly heated up to the burning point, and preventing its disturbance afterwards. The arrangement is very simple, and easily applied to steam-boilers. As no smoke appears, at first sight it strikes the observer as if the coals to be burnt were thrown down its short chimney until it was completely choked; but on looking more closely, he perceives that this strange looking little chimney is the "feeding funnel" by which the Anthracite is propped up in a tall heap over the fire, and resting on it, where it remains with its lower stratum growing hotter and hotter till it kindles; then, as the burning mass on the grate beneath is gradually consumed, the layer just in contact with it sinks quietly into its place, where it in turn becomes fully ignited, and so on. The redhot burnt air, (not flame,) is carried round about and through the steam-boiler by flues as usual; and then flies off, without a particle of smoke to mark its progress, through the chimney at the other end of the furnace. Experiments recently made have ascertained that one ton of Anthracite, burnt in a proper fire-place, will raise as much steam as one and a quarter ton of common coke. This fact, therefore, places the latter fuel at a serious discount, even at present rates, as it would require 30s. worth of coke to do the work of 27s. of Anthracite.

A small iron steam-boat has been built for experiments with this fuel, and has been appropriately named the Anthracite. The construction of the furnace is the main novelty. In the first experiment upon the Thames, although the boiler is small, it sufficed to generate an abundance of steam; in fact, the engine was working at 45 strokes per minute, which is said to be something above the proper speed. The peculiarities of the fuel were very striking. Its power of conducting heat is so trifling, that the upper surface of the mass in the feeding funnel right over the fire gave no indication of the heat beneath; and when the fire-door below was opened for an instant, black coals rested on the surface of the red ones. The fire-bars are laid sloping away from the funnel, so that as the fuel descends it spreads equally over the extent of the grate without the aid of a stoker. No slag or fire-cake results from the fuel, and a few cinders which fall through the narrow bars still contain so much carbon that they are thrown into the feeding funnel again. The little " stoking-room" is from the absence of all meddling with the fire only of a comfortable temperature - a great advantage on a tropical voyage. The "firedoors" are never opened to feed the fire, as all that goes on upon deck through the funnel, (as millstones are fed through a hopper, but this does not hop ;) and, consequently, the fire is never half extinguished (as in ordinary fire-places) by a fresh supply, with the necessary evil results in addition, of steam checked, power lost, and smoke emitted. The combustion of the Anthracite goes on smoothly and equally, like that of the oil in Parker's new lamp, which is heated almost to the boiling, or rather burning, point, before it is inflamed in the wick. Mr. George Rennie, who seemed to take a great interest in the experiment, caused the fuel to be weighed during the trip, and found that the quantity for producing the effect of one-horse power for an hour was, 6 lbs.; but this, from the short duration of the experiment, can only be looked upon as an approximation.- Mechanics' Mag.; abridged.