The annexed engraving is a vertical section of an improvement in Hot Air Stoves, invented by J. M. Thatcher, formerly of Lansing-burg, Rensselaer Co., ?. Y., who secured a patent for it on the 23rd of March, last year. A is the outer casing of the stove, which consists of a cylinder of sheet metal, set upon a cast-iron base plate, B, below, which farms the ash pit, C. The fire-box, D, rests upon the baseplate. ? is the grate; F is an inverted circular dome of cast-iron having an opening through its centre surrounded by a rim, e which fits to the top of the fire-box, and having also another rim, a, which stands up from its outer edge ; it hae a number of small tubes, b, standing up from it, ranging in a circle around the lire-box. G is a short iron cylinder fitting close over the rim, o, and being supported by the dome, F, the space between it and the outer casing, A, forming an annular passage, H, it reaches to the same height as A. I is an inverted dome of cast-iron ; it has an opening through its centre, surrounded by a rim, C, which extends upwards in the form of a slightly conical tube, and has another rim,rf, extending upwards around its outer edge; it has a series of short tubes, ff, extending downwards from it, which fit over the tubes, b b, of the dome, F, and form passages through both domes, tubes, b b, supporting th upper dome. J is a damper ; ? is a sheet iron cylinder fitting over the rim, rf, the space between it and G forms an annular passage, L. M is an inverted dome, similar to F ; it has an opening in its centre surrounded by a rim, g, which fits over the short wide pipe, c. A series of tubes, i i, are ranged in a circle, passing through the rim, h. ? is a sheet-iron cylinder fitting over rim h, and is supported by dome M. There is an annular space, 0, between it and the cylinder, ?. ? is a circular plate of cast-iron, with an opening through its centre surrounded by rim,/, forming the chimney seat; it has a xim,k, extending upwards around its outer edge, and has a number of short tubes, 11, above i i, extending upwards, forming passages through the dome ; Q is a short iron cylinder fitting and resting on the plate, P, and running up to the same height as cylinders A & G, the space between it and ? forms an annular passage, R S is the chimney ; ? is an annular space ; V is a cast-iron plate, it fits down close to the cylinders, A, G, and Q, and has openings, m t?, communicating with H; one, n, which communicates with T, and a series, ? ?, which eommunicate by a series of tubes,pp, with the space, 0, the top of said space being covered and closed by a ring of metal, so as to close all outlets except through the tubes, ? ?. V is the cover of the stove, which fits to the outer casing, A, or to the plate, U. Y is a distributing chamber for the heated air ; q q are passages tor distributing the air. ? is a plate surrounding the foot of the fire- box, D, and through which the air is admitted to be heated, as shown by the arrows at r. ? is the grate ; kC the ash pit. When the damper, J, is closed the draught of the fire plays between the tubes, b b, ascends the annular flue, L, and then passes, between the tubes, ? ?, descends the annular flue, R and after passing between the tubes, i i, ascends to the chimney, S, its course being indicated by arrows. The air to be heated passes through openings, r, in the base plate, then rises up into the inverted dome, F, where it spreads, and part of it ascends the passage, H, passes through the openings, m m, to the chamber, Y, while apart ascends the tubes, b b,ff, to the space between the inverted domes, I and M, where it is again divided, part ot it passing up the passage, 0, through tubes, ? ?, to the distributing chamber, Y ; the remainder passes through the tubes, i i, and passage, T, to the Said chamber, and then through the passages, q q. During the ascent of the air it is thus brought into contact with an immense amount ot heating surface. The arrangement of cylinders described may be increased in number by the same mode of connection. As the heat is more intense near the centre of the stove, stronger currents of air are made to pass through the central passages. This is accomplished by making the sum of the areas of tubes, b b,f f, greater than the openings of m m, at the top of passage H, and the sum of the areas of passages, 0 T, greater than that of H ; this principle is shown by the relative size of the passages and tubes, near to and at a distance from the fire-box and smoke-pipe. The great and grand object of all stoves or furnaces for heating air to distribute through buildings—to keep the same at an agreeable temperature and in a healthy state is to have a large amount of heating surface and a low heat. If possible, the hot surfaces should never be above 100 Fah. Air passing over very hot iron plates—to use a common phrase, the meaning of which is well understood—is burned, and in that state is not fit for human beings to breathe. In many churches and public buildings the hot air iurnaces employed, are too small, hence intensely heated air deprived of part of its oxygen is thrown through the building, the effects of which are deeply injurious. More information may be obtained by letter addressed to Mr.Thatcher, who is now residing in Jersey City, N.J.