Conservatory, a house in a garden, contrived for sheltering and preserving the most curious and tender exotic plants, which in our climate will not bear to be exposed to the open air, especially during the winter season. These are generally large and beautiful structures, equally ornamental and useful.

The length of greenhouse must be proportioned to the number of plants intended to be preserved in them, and cannot therefore be reduced to rule; but their depth should never be greater than their height in the clear; which, in small or middling houses, may be 16 or 18 feet, but in large ones from 20 to 24 feet; and the length of the windows should reach from about one foot and a half above the pavement, and within the same distance of the ceiling, which will admit of cornices round the building over the heads of the windows. Their breadth cannot be in proportion to their length; for if in the largest buildings they are more than seven or seven feet and a half broad, they will be extremely heavy and inconvenient. The piers between the windows must be as narrow as may be to support the building; for which reason they should either be of stone or of hard burnt bricks. If the piers are made of stone, they should be 30 inches wide in front, and flopped off behind to about 18 inches, by which means there will be no corners to take off the rays of the sun. If they are of brick, they will require to be at least three-feet in front, but they should be in the same manner flopped off behind. Over the greenhouse may be rooms for drying and preserving seeds, roots, &c. and behind it a place for tools and other purposes; and both these behind, and the rooms above, will be of great use in keeping off the frosts, so that the wall between these need not be of more than two bricks and a half in thickness.

The floor of the greenhouse, which should be laid either with Bremen squares, Purbeck stone, or flat tiles, must be raised two feet above the surface of the adjoining ground, or if the situation be damp, at least three feet; and if the whole is arched with low brick arches under the floor, they will be of great service in preventing damps; and under the floor, about two feet from the front, it will be very advisable to make a flue of ten inches wide and two feet deep; this should be carried the whole length of the house, and then returned back along the hinder part, and there be carried up into funnels adjoining to the tool-house, by which the smoke may be carried off. The fire-place may be contrived at one end of the house, and the door at which the fuel is put in, as also the ash-grate, may be contrived to open into the tool-house, and the fuel being laid in the same place, the whole will be out of sight. Bradley advises, that the front of greenhouses, in the colder parts of England, be built in a sweep or semicircle, so that one part or other of it may receive the sun's rays all day. The use of fires must, however, be very sparing in this place; and it is not one winter in three or four that will require them in any part, only when the weather is very severe, and the frost cannot well be kept out any other way, this is an expedient that is good to have in readiness, as it may save a whole house of plants. Withinside of the windows, in front of the greenhouse, there should be good strong shutters, made with hinges, to fold back close to the piers, that they may not obstruct the rays of the sun. The back part of the house should be either laid over with flucco or plastered with mortar, and whitewashed, in order to prevent the frosty air from penetrating through the walls. When the greenhouse is wainscotted, the walls should be plastered with lime and hair behind the wainscot, to keep out the cold; and the wainscot, as well as the ceiling, and every part within the house, should be painted white, for the reflection of the sun's rays. There must be a number of trellises with forms of wood upon them, to support the pots of plants; the tallest to be placed hindmost, the lowest within four feet of the windows; and the rows of plants should rise gradually, so that the heads of the second row should be entirely above the first; and behind them there should be a space of at least five feet, for the convenience of watering the plants, and for a free circulation of air. It has been observed, that the placing of the euphorbiaceae, cereales, and other succulent plants among orange-trees, and other common greenhouse-plants, is always destructive of them, by making them receive an improper sort of effluvia, which plants of that kind imbibe very freely. They should therefore be placed in two wings built at each end of the greenhouse; which, if well contrived, will be a great beauty as well as use to the building. These wings may be made capable of a greater warmth also by more flues, and may be made to contain a hot-bed of tanners bark for the raising many of the tender plants, natives of warm climates.

Whilst the front of the greenhouse is exactly south, one of the wings may be made to face the south-east and the other the south-west. By this disposition the heat of the sun is reflected from one part of the building to the other all day, and the front of the main greenhouse is guarded from the cold winds. These two wings may be so contrived as to maintain plants of different degrees of hardiness, which may be easily affected by the situation and extent of the fire-place, and the manner of conducting the flues: the wing facing the south-east is evidently the most proper for the warmest stove; this may be divided in the middle by a partition of glass, with glass-doors opening from one division to the other. In each of these there should be a fire-place, with flues carried up against the back-wall, through which the smoke should be made to pass as many times the length of the house as the height will admit of the number of flues; for the longer the smoke is in passing, the more heat will be given to the house with a less quantity of fuel. The other wing, facing the south-west, should be divided and furnished with flues in the same manner; and thus different degrees of heat may be obtained, according to the seasons and the particular sorts of plants that are to be preserved. If there are no sheds behind these wings, the walls should not be less than three bricks thick; and the back part, having sloping roofs, which are covered with tiles or slates, should be lined with reeds, &c., under the covering. The sloping glases of these houses should be made to slide and take off, so that they may be drawn down more or less in warm weather to admit air to the plants; and the upright glasses in front may be so contrived as that every other may open as doors upon hinges, and the alternate glasses may be divided into two: the upper part of each should be so contrived as to be drawn down like shades, so that either of them may be used to admit air in a greater or less quantity as there may be occasion.

As to the management of the plants herein, Mortimer recommends the opening of the mould about them from time to time, and sprinkling a little fresh mould in them, and a little warm dung on that; as also to water them when the leaves begin to wither and curl, and not oftener, which would make them fade and be sickly; and to take off such leaves as wither and grow dry.

Green-Sickness (Chlorosis). See Index subjoined to Medicine.

Vol. VIII. Part I.

Green-Silver, the name of an ancient custom within Greenland, the manor of Writtel in the county of Essex in England; which is, that every tenant whose fore-door opens to Greenbury shall pay an half-penny yearly to the lord, by the name of green-silver.

Green-Wax, is used where estates are delivered to the sheriffs out of the exchequer, under the seal of that court, made in green wax, to be levied in several counties. This word is mentioned the 43rd Stat. Ed. III. c. 9. and 7 Hen. IV. c. 4.