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they are kept in a high temperature, both night

and day.

A luxuriant and healthy state is shown by a large substantial stocky stalk, and leaves of a dark green colour, with a purple or brown hue.

Excessive heat or cold in the atmosphere will be shown by a general stinted appearance in the growth of the plants, and by their being parched and withered at the tops of their leaves.

In the erection of a pinery, my first object would be to obtain as much light, and of the rays of the sun, as possible.

Secondly, to establish the means of keeping a temperature as high on cloudy days, or during the sun's absence, as during those of a clear and constant sunshine; and a bottom heat proportionate to the atmospheric heat, without the liability of its being raised much beyond it, or of creating obnoxious vapours.

Thirdly, to furnish a constant flow of fresh air into the house, rarefied to such a degree, that in its diffusion it may not reduce, or materially change, the general temperature; and in such quantity, that by its pressure, it may exclude and prevent the ingress of cold air.

Fourthly, to arrange and constitute such a bed for the roots, that the plant may grow with or without pots.

To establish the first object, the house should front the south, or as nearly so as possible ; the width be about twelve feet, and the length of any

extent that may be desired; the form and elevation of the roof as represented by fig. 1. plate 13.; the glazing of the north side to be close puttied, or what is better, copper lapped, to avoid many inconveniencies and injuries to which all the usual modes of glazing are exposed. I would have the panes of glass as long as possible, say from two to three feet, and laid so as to overlap each other without stopping, and the ends of the panes to be angular, as shewn by fig. 2. The two ends of the house and the front to be close glazed, as fig. 1.

Second. A brick wall to be raised nine inches withinside, the full length of the house, in the manner of a pit without ends, about eighteen inches, or two feet from the front and back walls of the house; the front to be about two feet high, and the back three feet; on these place bars of iron, of about two inches square, to reach from one wall to the other, in the manner of joists ; and over these, by way of a floor, place Welsh slates of the largest size, in such a manner that the lower edge of the uppermost may pass under the upper edge of the next, lengthwise, (which will be the reverse of their usual position on a roof,) this will admit superabundant water to pass off each slate; the ends of the slates may be laid so as to join even, and be closed with cement underneath the slates, to range from one end of the house to the other; place rows of steam pipes of four-inch bore, continued by turns at the ends, and connected with the steam boiler, on Hague's patent principle,

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as shown by fig. 3. These pipes may be suspended from the iron joists; and as they will require a graduated declination to conduct the condensed steam back into the boiler, the conducting end may be placed three or four inches from the bottom of the stage, and made to fall about an inch in each length of the house.

As heat always ascends with much greater force than it descends, and Welsh slate is a good conductor of heat, there can be no doubt but that by this method, bottom heat sufficient may be produced and sustained; and as there will be a space of from four to eight inches of air intervening, which is a slow conductor, the heat will be equalized.

To raise the heat in the body of the house, as it may be wanted, let a row of six-inch pipes be laid all around the inside of the house, within two inches of the walls of the pit, and be independently connected with the boiler, as marked B B B, fig. 3.

Third. Air jackets or boxes to be placed at intervals of three or four feet along the front pipes, as marked C C, fig. 3., and C, fig. 4.: these will be found to furnish air sufficient at all times, without the necessity of opening the glasses ; at any rate the front sashes may be fixed, and for a greater command of air in summer, casements or sliding sashes may be formed at intervals in the north side of the roof.

Fourth. Lay a bed of earth entirely over the glass or floor of slates, of from fourteen to eighteen

inches deep; and in this place the pots, or the plants without pots. The distance apart of plants in the bed should always be such as to admit the leaves to spread their full extent, without the plants touching each other when full grown. Or if it be thought that tan bark contributes either to the health, size, or flavour of the pines, this may be placed over the floor of slates of a due depth, instead of earth, and the pots plunged into it.

The space under the slate floor may be profitably appropriated to the growth of mushrooms, asparagus, sea kale, &c.

263

ESSAY

ON THE

NATURE AND APPLICATION OF STEAM.

It has long since been demonstrated, that steam is infinitely superior to every other medium for diffusing an equal degree of heat through any given space. Fire applied by one furnace or boiler to circulate steam through a range of metallic pipes, chambers, or boxes, will communicate a more equal degree of heat, to the extent of a mile or further, than it could be made to do 500 times repeated by any other means. The number of accidents which have occurred from imperfect construction, bad arrangement, and carelessness, have impressed most people who have heard of steam engines, with ideas of danger in the appropriation of steam for any purpose; but the improvements made in the construction and arrangement of an apparatus by Mr. Hague, and for which he has obtained a patent, must convince every person who will give it consideration, that there is less

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