Boilers. Many ingenious vessels and utensils have, at different periods, been invented, with a view to facilitate the process of boiling, and save the consumption of fuel. In the latter respect, Count Rumford stands at the head of those experimental inquirers, who have directed their labours to the benefit of society; yet must confess that there is still it room for improvement. One of the latest inventions in this department of domestic economy, is that of Mr. Tho. Rowntree, engine-maker, of Great Surrey-street, Blackfriars-road, who in 1798 obtained b o I tained a Patent for "a new method of applying fire for the purpose of heating boilers and other vessels, where heat is required." But as the Patentee had not given a clear specification, from which an ordinary tradesman could have constructed a furnace on his principles, without any farther explanation, his Patent was declared void, after a trial before Lord El-don and a special jury, on the 3d of November last, and has consequently become public property. These proceedings, however, have been attended with a good effecf, as the obscure account published by Mr. Rowntree, has been more clearly defined by the evidence given in Court, especially by that of Mr. Hindmarsh. We shall, therefore, present our readers with the specification communicated by the Patentee, and accompany it with the necessary illustrations.— The following is a literal abstract of the inventor's description :— "For heating of coppers, boilers, furnaces, ovens, and stoves, my fire-place is much smaller than heretofore made use of for the same sized copper, boiler, furnace, oven, or stove. Instead of placing my fire-place, according to the common practice, immediately under the boiler, or other vessel, I place it at the front, side, or end, as I see most convenient, in such a manner as to oblige the flame to rise in the front, side or end, and pass all round the vessel, etc. while at the same time it strikes the bottom of the vessel, etc. without suffering the flame to pass off in a flue, or flues, as it usually does in the common way, and by that means sending the heat into the flues, instead of its being used where it ought to be, namely, on the vessels, etc; this, my method' effectually prevents; for, by means of a small perpendicular, or other opening, into a box or trap, which I call a reservoir, and which I place horizontally, or diagonaly, as the situation may require, and is made of iron, brick, stone, or any other material capable of bearing heat, where a valve is placed riding on centres or otherwise, and standing in a diagonal or other direction, as is found most convenient, the flame is returned or impeded in its progress to the chimney, and made to descend below the bottom of the vessel, and pass out at the bottom, top, or side of said box, trap, or reservoir, into the common chimney. This reservoir is placed between the vessel, etc. and the chimney. To the ting, which admits the flame into the reservoir, are affixed, whe necessary, sliders, registers, or stops, which serve to increase or diminish the heat. The valve in the reservoir is for the same purpose in another degree, which more immediately appertains to increasing or diminishing the draught, which it does by moving the said' valve into different positions, as the speed of the operation may require."

It would be needless to state the particulars of the evidence relative to the effect produced by the new invented furnaces, in heating boilers, etc. as well as the great saving of fuel, which was proved to be more than one-tliird, and in some cases nearly one-half, of what is usually consumed in furnaces constructed on the old plan. Hence we shall communicate only the substance of Mr. Hindmarhs evidence, which greatly tends to illustrate the principles of the invention. This, he conceives, principally consists in the three following circumstances:

1. In the peculiar mode of constructing the furnace, or setting the boiler, and of placing the lire, not immediately under, but a little in front, or at one side of it, whereby the flame and hot air can get access to every part of the vessel, and not only strike with force against its bottom, but also with equal effect reverberate against, and violently embrace its sides, and whole external surface; unlike every former contrivance, the most perfect of which could only cause the flame and hot air to act partially upon the bottom and sides of the vessel.

2. In the elevated situation, and smallness, of the aperture leading from the furnace towards the chimney; whereby the flame and hot air are impeded in their progress to the atmosphere, and compelled to tarry in the cavity of the furnace, and occupy every part thereof much longer than they otherwise would do. This effect in stopping, cheeking, and as it were arreting the flame and hot air, in their attempt to escape into the atmosphere, Mr. HindmaRsH considered as not only new, but singularly beneficial; for, by this means, the flame and hot air are detained in the very place where their presence is most wanted, and constrained to give forth their energies with an impetus against the bottom and sides of the vessel to be heated: whereas, in none of the furnaces heretofore erected, was any effectual slop interposed between the fire and the chimney, to cause the flame and hot air to dwell under and round the sides of the vessel; but they passed rapidly off into the atmosphere, either by a direct communication through the chimney, or indirectly, but almost as speedily, by flues ; or else by a drain (as it is called), the aperture of which is equal in dimensions to that of the chimney itself,

3. In an open space between the furnace and chimney, called by the Patentee a box, trap, or reservoir, and intended as a receptacle of the flame, hot air, and smoke, after they have quitted the furnace', and passed through the small aperture as above described. This space, or reservoir, for the flame, hot air, and smoke, being closed at the top and external sides, and open only at the bottom outwards, for the purpose of permitting the smoke, etc. to pass off into the chimney, still farther checks and detains the flame and hot air in the furnace; and being itself constantly full of warm air, smoke, etc. causes the heat to be reverberated against the sides and bottom of the v.( or boiler, and effectually prevents the admission of the cold atmospheric air from the chimney, which, on the old plans of construction, is found by experience to rob the furnace and vessel of more than half the supply of heat which any given quantity of fuel is capable of yielding. The valves, sliders, and dampers, are not essential parts of the invention, but merely as regulators; which, in many cases, may be altogether omitted, without detriment to the operation of the fire.

Although Count RumfoRd has successfully extended bis researches to discover the. most economical plan in the management of fire, and the generation of heat for culinary and other purposes, it does not appear from his writings, that he had a distinct conception of the new method suggested by Mr. Rowntree, till alter the. enrolment of his specification in May 1798. Nay, says Mr. Hin-dmarsh, the Count evidently takes it for granted (see vol. II. p. 73, of his Essays), and even reasons on the fact, which he there supposes to be unavoidable, and beyond remedy, that the fire cannot be made to impinge against the sides of a vessel with the same force and effect as against the bottom : which is a plain proof, that at the time of writing that essay, he was totally unacquainted with Mr. ROWN-tree's method of applying and managing the fire; in which the very effect which the Count considers as a desideratum in science, and which appears to have been one grand object of his philosophical pursuits, is now in a great measure completed.