GREENHOUSES, as nosy built, serve not only as conser vatories, but likewise as ornaments of gardens; being usually large and beautiful structures. sometimes in the form of galleries, wherein the plants are handsomely ranged in cases. See CONSERVATORY.
The greenhouse is a sort of building designed for the purpose of preserving various kinds of exotic: shrubs, &e,, through the winter season, and for grossing and those kinds of plant, which are too tender to live in the open air. It is fronted and covered with glazed frames, but the aid of artificial heat is not necessary in intensely cold Weather. It is ielvisable, however. in constructing., such houses, to erect flues to use occasionally. which may prove serviceable, nut only in severe frosts, Ind also in moist, foggy weather, when a Moderate fire will now and then dry up the daml,s, w hich would otherwise prove pernicious to many of the tender kinds of plants.
It differs from the conservatory chiefly in this circumstanoe, that the plants, trees, or shrubs, arc in pots or tubs, and placed upon stands, frames, or stages, during the winter, to be removed to proper situations in the open air, during the hut summer season ; while in that, there are beds, borders, and clumps, laid out in the ground-plan. and made up w ith the host earthy materials, to the depth of three or four feet, in which the shrubs, trees, &e. are regularly planted ; the whole of the roof being removed during the summer to admit fresh air, and replaced on the approach of the autumn, to remain until the following summer.
Greenhouses should stand in the pleasure-ground, near the house, if possible, upon a somewhat elevated spot, full to the south, and where the sun has access from its rising to its setting. These buildings are generally of brick or stone, having the fronts and tops almost wholly of glass-work ; and ranging lengthwise cast and west. They are generally con structed upon some ornamental plan. As to the general dimensions, in respect to length, width, and height, they may be from It) to 50 feet, or more, in length, according to the number of plants to be contained ; and in width, from 10 or 15 feet to :20 feet ; but, for middling houses, 15 or IS feet is a sufficient width ; and in height in the clear, nearly in pro pot tion to the width.
The walls on the backs and ends, particularly the former, should be earlie• up two bricks thick ; and if more than 15 feet high, two bricks and a half thick ; at one end of the back wall, on the outside, a furnace may be erected for burn ing fires oceasionally, communicating with flues within, ranging in two or three returns along the back wall, having One tine running along the trout and end walls, raised wholly above the door of the house.
The fronts of the buildings should have as much glass as possible, and wide glass doors should be made in the middle, both fur ornament and entrance, and fbr moving in and out the plants. It would also be convenient to have a smaller entrance door at one end ; the width of the windows for the glass sashes may be five or six feet: and the piers between the sashes may be either of timber, six, eight, or tell inches wide, according to their height, or it' of brick or stone work, two feet wide at least, sloping both sides of each pier inward, that by taking off the angles, a free admission inay be given to the rays of the sun. For the satine reason, the bottoms of the sashes should reach within a loot of the floor of the house, and their tops almost as high as the roof; and it' brick or stone 'tiers two feet wide, shutters may be hung on the inside, to fill back against each pier. The roof may be either wholly or only half glass-work, next the front ; the other half slated, especially if the upright or front piers are of timber ; and the shutters to cover the top glasses may be so contrived as to slide under the slated root': where the piers are of brick or stone, it is common to have the roof entirely slated or tiled ; but slating is the most ornamental for at hall' or whole root'; an I the within should be w bite; which, as well as the w hole inside must be well plastered and white-washed, so as to render it clean and neat.