greatest distance at the lower point h2 (which in this case is th of the diameter of the external cylinder, but may be varied according to circumstances,) it follows that in whatever direction the engine revolves, the area of that part of the pistons which is acted on by steam and vacuum gradually increases, so that the principle of expansion is carried out to its full extent, without the aid of expansion valves and gear. The steam passing through the eduction passage Qis conducted by the eduction pipe R to the condenser S. Tis the injection slide, placed at the lower end of the eduction pipe, and conducting the water up the pipe, so as to act fully on the steam in passing downwards; it is worked by a lever an rod connected to the handle U, which is placed in proximity with the other starting handles H and P. V is the blow-through valve. W is the air-pump, which is a double acting one. The interior arrangement of its valves, &c. is shown in figure 2. It has a metallic packed piston which is worked from the main-shaft by a crank and connecting-rod, and the piston-rod is kept parallel by two slide-guides bolted on the air-pump cover. X is the hot well, and Y the discharge passage. The pumps are worked from the main shaft by an eccentric c, connected by rod and lever to a rocking-shaft d, on which are keyed two levers e and f, which are connected by rods to the pumps g and h. The pump g is intended for the bilge water (in the case of marine engines) and the pump h, for feeding the boilers. The latter has its valve chest j bolted on the hot well. The following able "Analysis of the Economy and Power" of this Engine, as compared with other engines, has been obligingly furnished to us by the inventor, Mr. Borrie. MR. BORRIE'S PATENT REVOLVING STEAM ENGINE. mean area of the piston; the distance the centre of pressure of the piston travels; the direct, opposite, and effective, pressures on the piston; the number of times to which the steam is expanded; and the number of lbs. lifted one foot high, in passing through each of these divisions. The external cylinder is 3 feet 6 inches diameter, and 1 foot 6 inches long inside; and the greatest distance between it and the internal cylinder, is 7 inches. The steam is supposed to be at a pressure of 261 30 lbs. on a square inch, above the atmosphere, and the vacuum to be equal to 12 lbs. on the square inch, the shaft making 50 revolutions per minute. The direct pressure or force of the steam to turn the engine round in the required direction, is marked on the Table + pressure, and the opposite, or force resisting the motion in that direction, pressure: of course, their difference, is the effective pressure. From the Table the following results are obtained :- 1 Number of lbs. raised 1 foot high, by the revolution of one piston, 10980. The quantity of steam consumed by a revolution of one piston, is 1944-2 cubic inches. Number of pistons Steam required for one revolution Steam at 30 lbs. pressure on a square inch above the atmosphere, is 609 times the volume of the water of which it was generated, therefore, 4 7776 8 cubic inches. or 1095 cubic feet the quantity of water required for steam, per minute, 1892 638.5 quired for the common engine, as for the revolving engine, and consequently, only about one-third of the fuel would be required for the revolving engine, as would be required for a common reciprocating engine of the same power. =2.96 times the evaporation re PETER BORRIE, Engineer, 8, Princes-square, St. George's East, London, March, 1844. SMOKE-PREVENTING FURNACES. Sir,-At a time like the present, when remedial measures for the abatement of the Smoke Nuisance are so prominently before the public, every information really tending to elucidate this important subject must prove highly beneficial to manufacturers and the community at large. The means by which this desirable object may be attained have been long partially understood, that is, that it may be effected by admitting air to the burning mass of fuel, and the aëriform products of such fuel, whether wood, coke, or coal. Watts admitted air; Parkes admitted air, and smoke-burners in general have admitted air for 50 years past up to the present time; in short, every clever stoker will assert that he can burn smoke by leaving his bars a little bare, or allowing his fire door to hang ajar a short while after firing. What mystery, it may be asked, is there, SMOKE-PREVENTING FURNACES. then, in "smoke burning ?" The whole mystery consists in the mode of supplying the air, a matter so ably discussed in your valuable journal, by C. W. Williams, Esq., and so scientifically treated in his work on The Combustion of Coal, and the Prevention of Smoke, that I deem it superfluous to do more than notice briefly, that, as every measure of coal-gas, say every cubic inch, requires the enormous quantity of ten cubic inches of air, to supply the needful quantity of oxygen for its complete combustion without the evolution of smoke; and in like manner every cubic inch of cokegas, or carbonic oxide, requires 5 cubic inches of air for the same reason, it becomes almost self-evident that the best, indeed the very best, mode of admitting that air into the furnace, to effect its mechanical diffusion, in the hot atmosphere of gaseous products, is to divide it into numerous small jets or films, as first claimed by Mr. C. W. Williams's patent of 1839, and afterwards* by Mr. Samuel Hall in 1841, 1842. To show how much misconception exists on this subject, we have only to refer to the Mining Journal of last Saturday, wherein a correspondent, signing "A Manufacturer," addresses a letter to the Editor, dated Birmingham 3rd inst., in which he states that Mr. Muntz, of Birmingham, has "effectually accomplished what he thought was impossible,-viz. to consume the smoke from his 'muffles,' and this he has effected by Mr. Samuel Hall's patent." Having had several communications with Mr. Muntz, and heard his evidence before the select committee on Smoke Nuisance, in July last year, I feel assured that the above statement is incorrect. Mr. Muntz is well satisfied of the possibility of getting rid of the smoke from muffles, but he is not so well-assured that it will ever be attended with economy; and in regard to some particular processes in which these muffles, or annealing furnaces, are used, it is generally believed, that the carbon, &c. of the smoke is rather beneficial, than otherwise, in its effects on the metals within the muffle. Then, in the next place, we "Mr. are informed of the plan being Hall's patent," whereas he has a plurality. * Mr. Hall asserts that he has a prior claim for jets of air: if we admit he has a prior claim, the question naturally arises, by what law does he reclaim "jets of air" in 1841, 1842? 263 of "smoke-burning" patents, dating 1836, 1838, 1841, and 1842. But it so happens that the plan adopted by Mr. Muntz, by Mr. Gillott, steel-pen manufacturer, and by other parties in Birmingham, is not "Mr. Hall's patent," but merely a revival of the plan employed twenty-six years ago by Messrs. J. and P. Taylor, of London, of which I shall now furnish full particulars, from Thomson's Annals of Philosophy, vol. 12, for 1818, not doubting it will be read with considerable interest. It is as follows: On the Construction of Fire-places to Steam- 72, Upper White-cross-street, May 6, 1818. The annexed sketch exhibits the construction which we have lately used in the erection of fire-places to steam-boilers, and which seems to combine some advantages, so as, perhaps, to render it worthy a place in your journal; at the same time we are aware that there is little in it that can be called absolutely new. We were desirous in the first place to remove the fuel from the possibility of actual contact with the bottom of the boiler, which sometimes happens from the carelessness of the men; and still more to avoid, if possible, the injury accruing from the sudden influx of large portions of cold air from frequent opening of the fire-door. The contraction caused by this sudden diminution of the heat, is apt, in some cases, to disturb the joints of the plates, where high degrees of temperature are used, and to render them leaky. We have avoided both these evils, by removing the fire from under the bottom of the boiler, and placing it, as in the drawing, in a furnace, at one end, whence the flame reverberates through a flue passing under the vessel to be heated. As the cold air, which at times may be admitted, comes first into immediate contact with a mass of heated brickwork, and is mixed before it passes through the opening into the flue, by which the whole is, as it were, wire-drawn together, so united as to render the changes of temperature more gradual. The front of the furnace is provided with an inclined hopper, as shown in the engraving, (fig. 1), which is to be kept full of coal at all times, preventing the passage of any air that way, and the fuel may be occasionally pushed forward into the furnace without much break ing through it. This mode of feeding boiler fireplaces has been used before, and with advantage, and particularly where the coal is of such a quality as not to cake much, in which case it has been found that it supplies |