ON THE CONSTRUCTION AND HEATING OF HOT- HOUSES. 
255 
It consists of a bar of iron made in shape as shown in the annexed figures 
a a, or in any other ornamental shape that may please the proprietor. This iron 
swings on a pivot fixed in the rafter, as b b. 
The upper sashes of the roof are of course made light, so that they can be 
easily raised, as c. On that part of the light where the bar works, is fixed a plate 
of thin iron, c, of breadth and length enough to prevent the bar from coming in 
contact with the wood of the sash, and which being oiled would allow the bar to 
slide easily. 
Attached to the end of the bar is a cord or thin chain, which is either allowed 
to hang down to the back wall, or be fixed in any other way most convenient. 
If a cord is used, loops will be necessary, to catch upon hooks fixed in suitable 
places, so that when the light is open it may be kept in that position ; if a chain 
be used the links will answer the purpose. 
This system has, however, its disadvantages. First, the elevation of the 
lights would admit the air in too abruptly, which, if cold or frosty, might injure 
the plants ; and secondly, in times of high winds no air could safely be given, or it 
would be liable to lift up the lights and break them ; neither of which objections 
can be raised against sliding the lights. 
Thirdly. The probable cost of erection. Some idea may be formed of the 
cost of erecting a wooden house, by calculating according to the prices named 
vol. 2, page 84, and vol. 1, page 130. And a little on the cost of one 
constructed of metal may be gathered from a paper on the subject in the Horti- 
cultural Register, vol. 2, page 105, which was furnished by Mr. Waldron, a 
gardener of considerable experience. The principal cause of metal houses not 
answering, he attributes chiefly to their bad construction, being often built by 
persons totally unacquainted with the advantages or disadvantages vegetation derives 
from certain modes of construction. 
The house of which the annexed plan is intended to give an idea, contains 
12,000 and upwards of cubic feet. 
The aspect to be recommended for a house of this kind used for fruit, is to 
receive the full sun at eleven o'clock in the day ; and be so situated as to have the 
sunshine from four o'clock in the morning to eight o'clock in the evening. 
. The uprights in front, a, are three inches wide and half an inch thick, set 
