No. 4.] GREENHOUSES. 387 



form the upper side should be sloped so that the water will 

 run off quickly, as in Fig. 5, as with water standing contin- 

 ually on the siu'faoe they will rot out very quickly, no matter 

 what the material may be. 



I*osts. — The modern glass structures for growing plants 

 are made of such light material that few posts, except those 

 for the corner, the door posts and ventilator frames, are 

 used, the main i)art of the structure being supported by light 

 gas pipe three-quarters to one and one-half inches in diam- 

 eter, as in Figs. 2, o and 4. In some cases iron frames are 

 used when the structure is very light, consisting only of the 

 frame and gas-pipe supports, the sash bars and other wood- 

 work resting as a shell upon the iron supports. 



/Sash Bars. — The form of sash bars most in use is shown 

 in Fig. 12, having drip gutters at a, to catch the drip as it 

 runs down the glass and carry it to the plates and walls of 

 the house. Upright sash bars should be made without 

 this drip gutter. The sash bars are supported by perlins 

 (Fig. 11), which in turn are supported by gas pipe or light 

 lumber. 



Perlins. — In many cases angle iron is used as perlins, 

 which is much more expensive, but more durable. 



The ridge (Fig. 9) may be a plain board, six to eight 

 inches wide, or, better, one formed out of two-inch lumber, 

 with a groove ciit for the support of the sash bars and ven- 

 tilators. 



Plates (Figs. 6 and 7) are made in many forms, but, as 

 with the sills, should always have a sloping top to carry 

 away the water quickly. Fig. 7 represents a very good 

 plate, consisting of a two-inch plank eight to ten inches 

 wide, spiked on the top of the posts or frame, the sash bars 

 being fastened to the upper edge. To avoid shade from the 

 plate on the south side of the house, some houses are built 

 by having the upright sash bars meet those of the roof and 

 wall, the upper range of glass shutting over the lower, so 

 that the water will run away from the front wall. When 

 iron frames are used, the front wall may be out of perpen- 

 dicular from four to six inches to aid in this discharge of 

 the drip. Another means of carrying the drip away from 



