It has been mentioned, that stoves are liable to the objection of sometimes causing an unpleasant sensation from the air becoming over-heated, or, as it is termed, burnt. This may be obviated by heating the air destined to circulate in the apartments by steam, instead of employing the direct action of the fire. An apparatus of this description, patented by Mr. Stratton, is shewn in the following figures. Fig. I is an elevation, and Fig. 2 a section of the apparatus. It consists of an exterior tube of copper a, Fig. 2, within which is a smaller tube b of equal length, soldered to end plates c c, forming thereby a steam-tight vessel, surrounding the interior tube b. d d is a spiral apparatus of copper, coiling round the upright rod e; the periphery of this spiral exactly fits the interior tube b, so that no air can pass up or down without taking a winding course through the spaces formed by the spiral. f is a semi-globe of copper, perforated with holes ; and g g are two moveable plates, in which are cut oblong apertures, so that when the boles in each coincide, the air has a free passage through them ; but when they are moved by the lever h, so that the holes in one are covered by those in the other, the passage is stopped, and the air ceases to flc v. i is a steam pipe, for the purpose of admitting steam from a small boiler; and j is another pipe, for allowing the water formed by condensation to run back into the boiler or else where. Steam being admitted into the compartment formed between the two tubes by turning the cock, instantly heats the interior tube b, and (by radiation) the spiral d d, by which the air already filling the tube is expanded, and rises by its diminished gravity, escaping into the open atmo sphere through the holes in the cap f. The air underneath rushes in to fill the partial vacuum, and in its turn becomes heated ; by this means a constant current can be kept up so long as the corn partment is supplied with steam ; but this current would, in an un impeded passage, be much too rapid in its motion to become sufficiently heated for the pur pose intended. The spiral d d is therefore introduced, which causes the air (as we have said) to take a winding course, and thus traverse the whole heated surface of the spiral before its exit into the air. By this con trivance the air is made to traverse over a considerable surface of heated material, while the steam required to act therein is confined to a very short vessel, and, con sequently, has but a small portion of its surface exposed uselessly. It may be cased in wood or other non-conducting material, if de sired, for ornament or any other reason, without any diminution of its effect in warming the apart ment.
The following simple and in genious air stove is the invention of Mr. Perkins, of Fleet-street, and the engraving represents a stove upon his plan, which was put up on the premises of Messrs. Coe and Moore, printers, Old Change. Fig. 1 represents the stove, flue, and building, in which it is fixed. Fig. 2, a continuation of Fig. 1, on a smaller scale, ex tending it above the roof of the building. The letters of reference designate similar parts in each figure. The stove a is of a cylindrical form, fixed vertically in the brickwork it is closed above by the lid b, which is removed as often as may be required to supply the stove with fuel (coke is pre ferred). c c is the flue, which is a tube of wrought iron, excepting that curved portion immediately connected to the tUrnace cylinder, which is of cast iron. d is the ash pit. At i is an elliptical aperture, for the supply of air to the fire, which may be admitted in a greater or smaller volume by wholly or partially removing the cover k. 1 is a furnace door, for affording convenient means ' for clearing out the ashes. The grating
on which the fuel is laid, is not fixed, as usual, immovably in the brick work, but is connected to the frame by hinges on one side, and held up on the other by a cross-bar, which rests on a button m. This button being turned one quarter round, the grating imme diately fella as a trap door, discharging all the fuel into the ash-pit, by which the fire is almost immediately extin guished without trouble. The stove is placed on the floor of the basement or cellar, which is kept thoroughly warm and dry, so as make it a good store room for paper, although it is ' under ground ; from thence the flue ascends through the ground floor n, the first floor o, the next floor p, and passes through the roof, as shewn. The flue for the smoke c c c is surrounded, as shewn, by a larger tube, at about 3 . inches apart, for the conveyance of heated air to the several apartments. To effect this, cold air is freely admitted through a large aperture r in the wall, which enters the chamber s, and im pinging upon a strongly heated surface, it immediately acquires a much higher temperature. To increase this effect, the curved cast-iron neck of the flue adjoining the stove is considerably flat tened or expanded, so as to expose to the ascending column of air a more extended surface of heated metal. The caloric given out by the burning fuel, instead of being chiefly carried off by the flue, as in ordinary stoves, is rapidly abstracted by the current of air, which air, thus heated, may be wholly or par tially given out into any one apartment, or distributed in the several apart ments, as may be desired (either for drying the printed sheets, or for warm ing the persons at work,) by a few sim ple valves or registers. These registers are made of two separate annular plates, sliding circularly on their flat surfaces one over the other. The lower one is fixed by rivets to the sides of the external tube, and the upper one lies on the lower one, and is made to slide over it by moving to the right or left a small handle, which projects horizontally through a slot mortice in the external tube. The size of the interstices in these plates is both alike, as shewn in the separate Fig. a. By these registers, it will be seen that the whole of the hot air may be confined to one apartment, or distributed over several. The aper tures through which the heated air flows into the rooms, are 10 or 12 inches in diameter, and each one is provided with a cover like a saucepan-lid 4 to prevent, at pleasure, the hot air from entering any particular chamber. In the upper most floor the flue of the hot-air tube terminates at w, about 3 feet above the floor ; from thence the smoke flue alone ascends, which first rises a few feet, then takes a horizontal course, and afterwards passing through the roof, the upper extremity is provided with a canopy or cowl to keep out the rain, and to prevent the smoke from being forced downwards by sudden gusts of wind. The premises before mentioned are thoroughly warmed throughout the winter, at as high a temperature as is consistent with the comfort of the persons employed therein, at an expense of less than nine pence per day for fuel. But one of the chief advantages that result from this apparatus, is the convenient and facile manner by which the heat can be augmented to the required degree in any apartment, for the purpose of quickly drying the freshly printed sheets of paper, an advantage evidently of the first importance to printers, as it enables them to print their work with extraordinary despatch. But when a stove of this kind is not employed for drying moist substances, the hot air should be first brought into contact with a vessel of water, to render the air sufficiently humid for healthful respiration.