GLASS STRUCTURES. 



69 



below the planks and are braced. The inside rows of posts 

 need not be quite so strong- as the outside ones and need not 

 be braced. When a house is not more than twenty-four feet 

 long it will not be necessary to support the roof in more than 

 one place. This is done by extending- two of the middle posts up 

 to the rafters. 



In figure 28 is shown a cross section of this greenhouse and 

 the way the sashes and rafters are joined at top and bottom. 

 The sashes are cut so as to fit tightly at the top and the 

 plate is bevelled a little, so as to allow water to run off 

 quickly. 



There are sixteen wooden shutters for covering the 

 sashes on cold nights. These are made the same width as 



the sashes but six 

 inches longer. One 

 cleat is put on the up- 

 per side at the end, 

 and the other on the 

 lower side at the end. 

 When put on, the up- 

 per cleat is against 

 the ridge pole which 

 leaves the shutters 

 clear for the water to 

 run off. They are 

 made of second fencing 

 matched and dressed. 



In this house there 

 is glass over the path, 

 which is not necessary 

 in the lean-to plan, 

 shown in figure 29, 

 where the sash is all on 

 the south side of the path. It is important to have crops 

 grown as close to the glass as may be, and this fact should 

 be carefully borne in mind. This style of house is suscepti- 

 ble of many modifications. It may be used as a lean-to on 

 the south side of the dwelling, where it may receive a little 

 heat from the house. Its limitations are about the same as 

 those of hotbeds. When such a house is intended for use in 



Figure 29 - 

 hotbed, 



3 x i H " • 



-Cross section of lean-to greenhouse 



