APPENDIX.

ON THE FORCING OPERATIONS OF THE GARDEN.

UNDER the term of forcing, are comprised all those processes which are begun, carried on, and perfected by the stimulus of artificial heat, whether that heat be produced by the power of fire, acting through the channel of smoke-flues, or by the medium of hot water, and by beds of tan, fermenting leaves, or stable manure, with or without the assistance of hot linings. Direct sun-heat, whatever be its power, is not considered as an instrument of forcing, although, in point of efficiency, it is incomparably the superior agent. We conform to terms, while we admit their improper application.

Solar heat, were it always present, would be more than sufficient to carry on every operation suitable to the various seasons of the year; but as it is not under our control, or at our command, it becomes needful to excite a degree of artificial heat from radiating surfaces, which shall approach to a medium, (or mean,) between that of the utmost power of the sun at mid-day, and the greatest degree of cold during night, both acting through glass, upon an enclosed atmosphere. This definition is, perhaps, little more than an approximation to the fact; nevertheless it is quite certain that, in a clear day of mid-winter, the power of the rays is excessive far exceeding that (speaking comparatively) of climates within the tropics*, or which is manifested during the hottest seasons of our latitudes. It is by no means unusual to see the mercury in a closed stove raised in the shade to 105-110°, while the external atmosphere is frosty; whereas in August there might be some difficulty to raise the internal temperature of a house to 100, at the very moment when the exposed instrument marked 80°. This is one of the mysteries of light;

"It is not uncommon in the neighbourhood of London for a thermometer placed in the sun to rise 50° of Fahrenheit above one in the shade. At Cumana, Hümboldt never found the sun's rays to have the effect of raising the thermometer more than 6° or 7°. Nearer the pole the energy of the solar rays appears to be still greater than in this climate. Between latitude 80° and 81°, Captain Scoresby states, that the thermometer was 18° below freezing on one side of the ship, whilst on the other the pitch was heated to a temperature of 90° or 100°.”—Penny Cyclopædia, Art. Hot-houses.

it is one among a thousand which challenges inquiry, and claims “the superlative of praise."

Having thus generalized, the first subject which demands particular notice is:

THE VINERY.

This is the most important erection of the forcing department, and in its structure varies exceedingly. It is proposed, in the present article, to assume as a model a house erected for the express purpose of forcing an early crop of grapes upon vines in pots, to be succeeded by another later, or July crop, from vines grown in the house, and trained horizontally under the glass. Every amateur ought to be acquainted with the method of erecting forcing houses; and were he himself to take tools in hand, make and frame, glaze and paint, the wood-work, while superintending the bricklayer, (who ought to be a handy, adroit, jobber, at day-wages, amenable to the will of his employer,) he would speedily ascertain how comparatively small an outlay need to be incurred.

The heating of the house, steadily and efficiently, is the most material consideration; because, before a brick is laid, the proprietor should have fully arranged his plan, otherwise he may find himself at a loss, and hampered, just at the period when his operations ought to commence.

After all that has been asserted and written upon steam and hot water, it should appear that a well-constructed brick flue is equally qualified, and with more economy, to produce an ample and durable radiation of heat throughout every square inch of the vinery. But if, with all the pretended disadvantages of the old smoke flue, the foregoing assertion has been borne out by experience, what will be said now, that a discovery has been announced which is calculated to produce the complete combustion of all the smoke of the furnace, at a very trifling expense, but with the saving of nearly half the fuel.

The invention is just published, (August, 1838,) and patents have been secured; but, what is more to our purpose, a friend, on whom the utmost reliance can be placed, has examined the furnace, seen it in full action, and proved its capability, under conditions apparently the most adverse, to substantiate its utmost pretensions.

In investigating one of the furnaces, he saw the fire charged with a quantity of moistened coals, which produced a complete cloud of smoke from the chimney. At that moment, with the door open, by merely forcing a volume of steam upon the coals, from a fan-shaped jet, decomposition was effected; the elements of the watery vapour acted upon the smoke, and by electrolytic attraction converted them into steam and carbonic acid, attended with the developement of much additional heat.

A small boiler could be added; or, what is better, a cast-iron furnace, of the simplest form, with a boiler attached to it, in the manner of the patent cooking-ranges, might be furnished with a steam-pipe, and its fan-like perforated jet, and be adapted to every flue with little expense *.

These are little more than crude hints, which may easily be improved upon; but, assuredly, if our hot-houses can be thus heated by flues, deprived of smoke, every advantage of heat and moisture, by means of vaporization from pans or troughs standing upon the flues, can be combined with the wisest economy of money.

Next in importance to the furnace is the slope of the glass lights. This ought not to be less steep than 40°, nor need it exceed 45°; it will, in the latter case, form a right angle with the back wall; which ought always to be made the standard of calculation. The solar rays will thus fall perpendicularly upon the glass, or nearly so, at the season of the vernal equinox; and thus, in early forcing, be pretty equally distributed over the vines between the rafters, conferring vital energy upon the foliage, and stimulating into activity every developement of the growing, as well as the fruit-bearing plant.

The most equable temperature of a vinery is promoted by adopting that method of laying the bricks which is styled cellular work, particularly at the back wall of the house. By this method the bricks are laid on their edges,-two lengthways, and one across the ends of the other two, leaving a space or cell between the four. The cellular wall is described and figured at No. 465, Section I, page 413, September. It economizes bricks; the building, though lighter, is thereby rendered more strong; and the plate of air contained within the cells, when once heated by fire, or by the sun's rays, retains its increased temperature during many hours. I have repeatedly had occasion to allude to this circumstance elsewhere; and having erected a house upon the principles thus detailed, can attest, upon experience, its utility during the rigorous frost of 1838.

Vineries differ in extent; but thirty-six feet in length, by seven feet in breadth, inside measure, are good proportions; the height of the brickwall must be such as to provide for the slope, and allow of head-room below the trellis, and then "it will be of little consequence whether the lights rest on a front wall, eighteen inches or two feet high; on a wallplate, over a glazed front; or, finally, descend to within a few inches

By suggesting this mode of adaptation, I deprecate any attempt to infringe upon the right of patent; but surely the proprietors will turn their attention seriously to the assistance which they may render to the proprietors of forcinghouses; now especially as foreign competition has materially reduced the prices of fruit, but not the expenses of production.

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above the surface of the ground. In the front and end walls four-inch work will be quite sufficient.

A house erected by Mr. Carrington, of Missenden Abbey, chiefly for vines in pots, is about fifty feet long; the lights slope nearly to the ground, and the rain which falls upon them, passes along a gutter-pipe into a sunk reservoir, close at hand. A tank is, in fact, an indispensable appendage. This vinery was at first heated by a single flue; in front of it is a trellis to support the pots: this flue now returns along the back wall.

The best building-materials are the cheapest. Thus, my vinery was built with the finest red bricks, made in the neighbourhood. About 6,000 will be required if the back wall be cellular; and these, at 40s. per thousand, cost 121. Fifteen bushels of strong, recently-burnt lime, and three or four times the quantity of gritty, road sand, will be required at the least; but these can be purchased and carted, the former at 8d. per bushel, the latter for a few shillings.

The timber should comprise battens, each two and a-half inches thick, seven inches broad, and twenty or twenty-one feet long. Of these the rafters and wall-plates will be constructed. The quality of the batten is generally very good; the wood is full of turpentine, and therefore durable. The cost, at 4d. per foot run, is 6s. 8d. or 7s. For the sashes, the plate on which the rafters rest, the door and frame, deals three inches thick are used. They are to be sawed into boards, one, one and ahalf, and two inches thick for the frames and bars of the lights; and into "stuff," four by three, for the jaumbs and wall-plate. A twelve-feet deal costs 6s.

The sliding lights will be double, in pairs; the lower range is to be fixed; not, however, by nails or screws, but by wooden stops, made to fall against the front plate. By pushing up the lights a few inches to relieve the stop, each can, as wanted, be slided down and removed. The upper lights, which overlap the rails of the lower range, may all be made to slide, being secured, and the opening regulated by spring catches; or the alternate lights only may slide, the others being secured by strong brass eyes, screwed into the side stiles, to receive pins, that pass into the rafters. By removing a pair of these pins, the light can be taken down without much trouble. In a word, for the convenience of painting and repairs, all should be made moveable without much trouble.

The lights should not be less than a yard, nor more than three feet six inches wide; the bars to be cut out of 14-inch stuff, an inch thick before planing; the rabates to receive the glass are half an inch deep by one quarter of an inch wide on each side of the mid-rib: this will admit of a sufficient bedding of putty.

Glass is now dear; in 1835, squares, (or, as they are styled, quarries,) 5 inches by 3, might be purchased in Water-lane at 6d. the square

foot, subject to a discount of 10 per cent. for money; subsequently, the price was raised to 7d., then to 9d., or more, without any discount. Putty costs about 16s. the cwt.; white lead, 5d. per pound; and linseed oil about 4s. 6d. per gallon.

Painting ought to be carefully attended to; and the first process, after knotting, (that is, covering the knots with a mixture of glue and red lead,) is to prime every part of the wood-work with the following materials: To each pint of the best linseed-oil, add three ounces of finely levigated litharge. Let it be perfectly ground, and intimately mixed, at first with a small proportion, and then by degrees incorporated with the whole, of the oil.

The priming tends to saturate the surface of the wood with an oil, which is rendered drying by its attraction of the oxygen of the litharge; and thus less real paint is required to cover and secure the wood.

The sashes must be primed only, before they are glazed; and when the putty has set and become firm, they may be painted.

All the wood-work within the house, and therefore the inner side of the lights, should be painted white,-twice in oil. For the external work a light drab, or stone-colour, is in every respect most appropriate.

In preparing white paint, one pound of the best white lead, ground in oil, will generally be found to take seven ounces of oil; with these a quarter of an ounce of levigated litharge is to be incorporated as a dryer.

The stone colour may be varied in tint according to fancy; but one of good appearance and sound quality is made by grinding together three drachms troy of the best Turkey umber, one drachm of red lead, and a quarter of an ounce or three drachms of litharge, in a sufficient quantity of oil, adding them to a pound of white lead, mixed up as the white paint, with seven ounces of linseed oil.

Green is a bad colour for outside work; it harmonizes with no one thing about it, and it possesses few of the qualities which constitute what is called "a body colour."

Many, if not all, the colours, can be purchased of oilmen or druggists, ground in oil, and of the consistence of white lead. If these be employed, little grinding with the muller and slab will be required; but the quantities and proportions must be regulated by trials.

When a suitable tint is decided upon, the work, after the priming has become thoroughly dry, is to be painted twice; each coat should be laid on evenly, and the covering perfected by labour with the brush and sash-tool, not by daubing with a volume of paint; which, instead of securing the wood, causes smearing and blistering, with much waste.

It must be remembered, that a coat of paint given every autumn repays itself; but two coats should be applied in the painting of the second season.