CONSTRUCTION OF HOTHOUSES. 287 



Of the Framing. 



The framing of hot-houses should be neat and 

 substantial ; of the very best materials, and well 

 put together. The rafters should be deep and nar- 

 row, arid not broad and shallow, a thing we uni- 

 versally find in all the old hot-houses. The strength 

 of any rafter depends on its depth. If it be nine 

 inches deep, and two inches thick, it is stronger 

 than if it were six inches square, and containing, of 

 course, double the quantity of timber. Two, or 

 two and a half inches is sufficient thickness ; and if 

 neatly dressed offon the lower edge, it will not ob- 

 struct much light* The depth may vary, according 

 to the pitch and width of the roof, from nine to 

 eleven inches ; but ten deep, and two and a quarter 

 thick, is a strong rafter. 



I have been thus particular respecting the size of 

 rafters, because on them depends the free running 

 of the sashes, which should move on small rollers, 

 and in the easiest possible manner, as a security 

 against the breaking of glass. The breadth of the 

 lights should seldom be more than three and a half, 

 or less than three feet. If the lights be too broad, 

 they are unhandy ; and if too narrow, there is an 

 obstruction of light, by an unnecessary number of 

 rafters. 



The sashes should generally be made of two inch 

 stuff; the styles and astragals, being narrow and 

 deep, in order to admit all the light possible. They 

 should be strengthened by one, or if necessary, by 

 two small cross bars of iron. There should gene- 



