The outer wall should be four inches in thickness; that of the inner, eight inches from the base to the trench plates, and four inches above-made in the form of a circle, of such diameter as shall leave a space of two inches between it and the outer wall at the nearest point. Make the recess in the walls front of the door as shown by ground plan, No. 1, and of the dimensions described under same plan. Apertures must be made in the base of the inner wall, as shown in plan No. 1, to give the cold air free ingress into the space between the walls, and carry off the heat radiated from the inside wall into the perforated hot air pipe, and also to prevent the outer wall becoming hot and heating the cellar, causing a waste of heat, damage to vegetables, etc.

After the foundation has reached the height of the furnace base, the cold air channel, which is constructed to conduct the air directly to the space between the inner wall and the cast iron ash-pit, should be covered by means of iron bars overlaid with brick.

Outside Walls, four incnes thick, for all sizes.

Inside Walls, eight inches thick, all sizes, to Trench Plates, and four inches above.

Eight apertures, eight inches high and two wide. in base of inner wall, for the passage of air between walls.

The entrance or man-hole door, should be built in the outer wall, as shown by ground plan, letter E, and a corresponding opening in the inner wall, for the purpose of entrance. On a level with the base, a covering, similar to that of the cold air channel, should be placed between them and the open space between walls, closed with brick, that the heat from the chamber may not escape through the openings.

Construct the inner wall, as shown in the sectional view, No. 2, allowing its line to follow outward, somewhat in the shape of the pot, for four or five courses, gradually receding until within two inches of the outside wall; from this point carry it uprightly to the level of the dome plate; then commence to draw in or decrease its size in the form of an arched cone, of such sweep, that when opposite the annular chamber, or ring of the furnace, it shall have a space of four inches between; carry this arched-shaped wall from eight to twelve inches above the furnace, according to its size, then place iron bars across covered with brick; finish by thoroughly and smoothly plastering the walls inside.

The outer walls are to be carried up as represented in the drawing, partially arched, and covered like the others; after the mason work has reached the height from which it is desired to carry the hot air pipes through the walls, place the ends even with the inner wall, and build them into it.

Also build in casings of sheet iron or tin in front of the clearing-out pipe and funnel, through both walls-two inches larger than the pipe, running through them; the ends outside are of course to be stopped with caps, in one of which a hole is made to admit the funnel.

The hot air pipes should be conducted from the highest point of the inner wall, as in sectional view, through the arch of the brick work; from which point they should gradually rise to the registers in the floor, always keeping in view the fact that the nearer the pipes can be carried to a perpendicular line from the wall of the furnace to the apartment above, the more readily and economically is heat obtained.

The size of the pipes and registers, and their general disposition, is a matter requiring the best judgment of the mechanic under whose supervision they come, and are determined by the size, position, and distance of the apartment from the furnace, and can not be subject to any fixed rule; as in two rooms of the same dimensions, we often use pipes and registers of different size, owing to their nearness or distance from the furnace in a horizontal line-their height above the basement-the relative position of other pipes, the purposes for which the rooms are to be used, and the amount of heat required, &c., &c. As a general rule, however, in rooms upon the first floor, whose dimensions are equal to fifteen feet square, and of ordinary height, use an eight-inch pipe, and registers eight by twelve inches; twenty feet square, ten-inch pipe, registers nine by fourteen inches; twenty-five feet square, twelve-inch pipe, registers ten by sixteen, or twelve by nineteen inches. For halls of ordinary size, use register nine by fourteen; teninch pipe. Adopt the same scale in rooms of different capacity.

If pipes or hot air tubes are carried into apartments above those of the first floor, they should be two inches smaller in size, than those used in rooms of the same capacity below; so that, should a lower room require a pipe of ten inches in diameter, that above would be eight inches, and still higher, six inches; supposing each room to be of the same size, and directly above the first.

In all hot air pipes that go above the first floor, a damper should be placed near the exit from the furnace, and kept closed when not in use, in order to economize the heat that would otherwise fill the pipes when the registers are closed.

It is often expedient to heat two adjoining rooms separated by a partition; in which case, it is our custom to use but one pipe for both; bringing it up to the partition, and placing a T or horizontal pipe across the top, projecting each side, into which registers are to be inserted, of a size corresponding with the rooms.

In double parlors, or rooms connected by sliding or folding doors, we usually place but one register, near their common opening, in case it is intended to use both apartments at once.

In many instances, it is required to heat rooms not in a direct line of communication from the furnace, and in which it seems difficult to introduce pipe without marring the building, or exposing them to view in their passage through other

rooms. In such cases an ingenious mechanic will generally surmount the apparent difficulty by taking advantage of closets, spaces between partitions, chimney pieces, &c., or, if either are impracticable, by carrying the pipes upright through the corner of the room and hiding its unsightly appearance by finishing in front with wood, painting it in representation of a column, or in such a manner as will best suit the style of the apartment. As a rule, however, we do not carry pipes above the first floor, except it is designed to heat an apartment for use during the day, as the heat from the hall register will keep the chambers comfortably warmed by leaving the doors opened.

The smoke pipe should be carried directly to the nearest flue, and should it be necessary to carry it horizontally to a considerable distance, surround it by a casing, or pipe of tin, three inches larger in diameter than the smoke pipe itself, and the waste heat that radiates from the smoke pipe, may be used to warm any adjoining apartment, by continuing a hot air pipe into the room and inserting a funnel register which we manufacture for that purpose.

The cold air box should be constructed of wood, smooth-planed inside and out. Its opening should be from the north or west side of the building; carry it along the ceiling to the furnace, then drop it perpendicularly down to the base of the cold air channel. This box should contain a damper or slide, which in very cold weather, or when the fire is first kindling, can be partially closed; but so arranged that it shall never entirely shut out the air.

In speaking of a wooden cold air box, we do not by any means consider it imperative that this material should be used in its construction, as we often conduct the air in a brick trench covered with flat stones, smoothly plastered and thoroughly cemented, below the level of the ground. This method, when the cellar is dry, has the advantage of permanence, and occupies no room; but it is an additional expense which all are not willing to incur, and is not reckoned in making furnace estimates.

Perforate one or two of the hot air pipes with holes, two inches in diameter, in the part which goes between the walls, for the purpose of carrying off the heat that is collected in the space between.

If the cellar is wet, carry out the base on which the walls are to stand one foot larger than the walls themselves; use hydraulic or Roman cement in its construction; lay the brick two courses, and place a liberal supply of cement between ; then, after the furnace walls are erected, carry up a barrier or guard wall from the edge of the brick base, a few inches above the level of the ground, and fill the intervening space between the barriers and the outer furnace wall with cement or clay; adopt also the same precaution around the trench; in fact, form a complete casing of brick, thoroughly cemented, all round the base of the furnace, which will prove a sufficient guaranty from water.

In public halls, or buildings where but a single register is required, carry up the inside wall to a perfect arch and lead the hot air pipe directly from the top, and use a hot air grate without valves, of the following sizes:

No. 3 Furnaces-Grates 22 inches in diameter, and Hot Air Pipes 18 inches in diameter.

It is frequently desirable to have square or parallelogram shaped grates instead of round; when this is the case, use those sizes where capacity in square inches will be equivalent to those given above.

In speaking of grates without valves, we wish it especially understood, that in no instance where but a single pipe is taken from the furnace, should registers with valves be used, or dampers placed in the hot air pipes; but the amount of heat required, should be regulated by the fire itself; or, if an outlet be deemed expedient, carry it off by means of another pipe, into an adjoining apartment.

DIRECTIONS for using chILSON'S PATENT WARMING AND VENTILATING APPARATUS. 1st. In building a fire in the furnace, open the damper in the smoke-pipe. 2d. Clean out the old coal and ashes from the ash-pit, and also from the levergrate; sift the old coal, ashes, &c., and preserve the coal siftings for covering over the fresh fire.

3d. Always keep the ash-pit, under the grate, clear of ashes; this done, there is no possibility of burning out the grate.

4th. Kindle the fire with a small quantity of either wood, bark, or charcoal. Dry hard wood preferable.

5th. When the kindlings are well charred, put on a small quantity of white ash coal, and when well ignited, (but before burning up clear,) add fresh coal, not exceeding six inches in depth.

6th. Close both the feed and ash-pit doors, also the small register in the ash-pit door, then close the damper, in the smoke pipe, as far as practicable to cause the fuel to be consumed slowly-or on the air-tight principle; this always to be done before the coal burns up clear.

7th. Cover over the fresh coal fire in moderate weather, with fine coal and the old coal siftings, keeping the draft in the smoke pipe well shut off; in this way, a fire may be kept for a great length of time without replenishing; thus greatly economizing in the consumption of fuel; but in extremely cold weather, do not cover over the fire with fine coal, but keep it bright, always checking the draft to keep the fire clear of clinker.

8th. Always have a large supply of cold air passing into the furnace. At no time have the damper, in the cold air-box, fully closed; even in very cold weather it should be at least one-half open. The milder the weather, the more fresh air to be admitted for ventilation.

9th. Never allow all the registers to be closed at the same time; and if the rooms become too warm, regulate and lessen the fire, and let there be constantly a free circulation of warm air from some, or all the registers; this is essential for the ventilation as well as warming of the rooms.

10th. Do not suffer the fire during the day, to get so low, before replenishing, as to require kindlings to bring it up.

11th. Where there is provision made for ventilation in the rooms, and ventiducts extending down to the floor, with apertures at the top and bottom, close the apertures at the top, and open those at the bottom, until the rooms become well warmed and ventilated, and when there is too much warmth in the rooms open the upper apertures, permitting the heat to run off, until the room becomes comfortable, then close the upper apertures; never open the windows or doors in cold weather to cool or to attempt to ventilate the rooms; if done, it will prevent the action or draft in the foul air ventiducts; there is also a liability to those sitting near the windows or doors to take cold, in consequence of the cold air falling upon their heads. The above directions are simple and easily followed, and if strictly adhered to, will be found very perfect in operation, and economical in the consumption of fuel, keeping the fire ignited a long time without replenishing, and giving out a large quantity of fresh, healthful, warm air, perfectly free from redhot iron heat.

These ventilating flues or ventiducts, should always be located in an opposite corner of the room, from that at which the heated air enters, and should be carried up separately to the roof of the building. They should be fitted at the top and bottom with a door or valve, whose capacity should be equal to that of the ventiduct into which it opens.

The best material for their construction is, thoroughly seasoned, sound pine boards, planed smooth on the inner surface, and put together with iron screws.

It is indispensible to attach an ejecting ventilator to the ventiducts at their terminus. In this way, down blasts are obviated, the rain excluded, and, whenever there is a wind, no matter what its direction, it produces, in a properly constructed ejector, an active upward current.

The arear of the flues for admitting fresh air, should exceed those of its exit by about twenty-five per cent.

BUSHNELL'S PATENT HOT-AIR FURNACE.

Manufactured by Ezra Clark, Jr., 61 Front street, Hartford, Conn.

BUSHNELL'S FURNACE is the only one constructed on strictly scientific principles, and bears any test either of theory or practice. Scientific gentlemen have endorsed its excellence, and successful practice approves and confirms their recommendation.

The radiating part of this furnace, being that portion which diffuses the heat, is distinguished from all others from the fact that the cold air is passed into the furnace chamber between horizontal cast iron pipes or tubes, inside of which the hot gas of the fire is circulating, and communicating its heat, as it passes off to the chimney; so that the cold air is brought in direct contact with the heated iron, and is actually heated before it reaches the inner chamber of the furnace. While the cold air is passing one way to be heated (between the heated iron pipes) the hot gas of the fire is passing the other way to be cooled, and thus the mean difference of temperature is kept the greatest possible at every point. The greatest amount of heat will be communicated in this way, by the least amount of iron surface; and as the radiator has a very large surface, it follows that more heat is extracted (from a given amount of fuel) than by any other invention yet offered to the public.

This furnace is so constructed that it clears itself of ashes and soot, never requiring to be disturbed, and consequently requires not as much care as an ordinary fire. A child can take care of it when in use, and it can stand from season to season, untouched, without trouble or expense, and be at any moment ready for immediate use.

Two kinds of pots are offered by the manufacturer, for use with this furnace; one similar to the most approved forms now in use, the other entirely different, and the invention of DR. BUSHNELL. It differs from all others in allowing the fire to be stirred above the grate, and through the opening by which the coal is entered. This throws up the dead coals and cinders, which are then easily removed, and, as the grate need never be dropped, the dirty process of riddling is avoided. No ashes escape, and the cloud of dust which usually envelopes the tender in all other furnaces, is no where seen in this, and no uncleanliness results from renewing the fire. The fire may be stirred and cleaned when it is in full action, as well as at any other time; the coals will never rattle down to choke the fire, but will of necessity, by this method of stirring, always be thrown up into a light open cinder, giving free passage to the draft and facilitating combustion.

This furnace is offered in the entire confidence that it is the best ever manufactured, and this bold assertion is warranted and proved by the favorable testimony of those who have used it. A TRIAL IS ALL THE PROOF RE

QUIRED.

Three sizes of furnaces are made, viz.: No. 1 with 17 inch pot; No. 2 with 20 inch pot; No. 3 with 24 inch pot; which are now for sale in most of the larger cities and towns in the northern states.

Orders for Bushnell's Furnaces will be promptly attended to, on application by mail or otherwise, to EZRA CLARK, Jr., Hartford, Conn.