The length of green-houses ought to be proportioned to the number of plants intended to be kept, or raised. Their depth in small houses should not exceed 12 or 14, and in large ones, 18 or 20 feet. The windows should reach from about 11/2 foot above the pavement to nearly the same distance from the ceiling, so as to admit of a cornice being constructed round the buildings, over the tops of the windows. The breadth in the smaller con-servatories ought not to be more than 5 or 51/2, and in the larger ones 7 cr 7/12 feet; as they will other-wise become heavy and inconvenient.
The floor ought to be paved with Purbeck-stone, or flat tiles, elevated 2, or if the situation be damp, 3 feet above the surface of the ground; it will also be advisable to carry a flue, about 10 inches wide, and 2 feet deep, beneath the floor, through the whole length of the house, and to return it along the back part, where it should be Carried up into funnels, for the purpose of discharging the smoke. In the inside, shutters should be made so as to fold back upon the piers, that the rays of the sun be not impeded. The inner wall of the building ought to be cither covered with stucco, or plastered with mortar, in order to exclude the frosty air. But, if the walls be wainscotted, it will be requisite to plaster the intermediate space with lime and hair : the ceiling and walls or wainscot ought, however, to be white-washed, so that the rays of the sun may be reflected throughout the building.
While the front of the conservatory is placed directly south, the two wings should be respectively arranged to. face the south-cast and south-west. Thus, the warmth of the sun will be reflected from one part of the green-house to the other, during the whole of the day ; and the front will be effectually guarded against the cold northerly winds.
In the 2d vol. of" Recreations in Agriculture,' Dr. AndersoN pro-poses to construct a green-house, in such a manner that it may be converted into a hot-house, without requiring any additional fuel. He therefore recommends the roof to be made of glass, placed in a sloping direction; and to fix perpendicular windows on the top of the front wall, so as to raise the lower eaves of such roof considerably higher than that of the slates would have been, without elevating the middle of the roof. According to his plan, the triangular, perpendicular wall should be completely covered with glass, through which the morning and evening sun may be admitted. In the country, or in houses unconnected with others, he suggests the propriety of bringing perpendicular windows closely down to the floor, both on the east and west ends, in order to receive the benefit of the rising and setting sun.
With respect to the conversion of this structure into a stove, or hothouse, Dr. AndErson supposes it to be erected close to the kitchen chimney of an inhabited house. At a small distance from the bottom of the chimney, there is to be made a communication with a flue, or stove, which passes beneath, and rises on the opposite side of the green-house, where an appropriate tile is suspended from a lever which, by means of a cord fastened to its extremity, may at pleasure drop this cover on the top of the tube or flue, and thus prevent the smoke from ascending; the bottom of the cover being lined with pieces of thick cloth, so that it may apply closely and become air-tight. A valve is likewise placed in the chimney, which turns on a pivot, so as either to allow the smoke a free passage, or to impel it into the flue, whence, after parting with its heat, it is either suffered to escape at the top, or is reverberated, accordingly as the covering tile before alluded to, is shut or opened.
For a more ample account of this project, we refer the reader to the 2d vol. of Dr. Anderson's instructive work above cited, where it is illustrated by cuts. - We have here given an outline of his plan, because it is ingenious, and may lead to farther improvements.
With respect to the management of plants in green-houses, Mor-timer recommends occasionally to open the mould in Which they are set, to scatter a little fresh earth on the pots, and over this to lay a little dung. It will also be advisable to water them, when the leaves begin to curl or wither; and to pluck off such as are decayed ; but these operations should not be too frequently repeated. - See Hot-house.