CONSTRUCTION AND HEATING OF GLASS HOUSES. 69 



bricks are desired, see that they are exactly the size of the others 

 you are using, and enameled on such of their several surfaces as 

 to enable you to get one of the bonds above described. A good 

 mortar for greenhouse walls is composed of two parts of clean 

 sharp sand and one of good Rosendale cement. 



Upon the foundations, which usually extend above the ground 

 to about two feet six inches, a heavy cast iron sill is set in equal 

 parts of Portland cement and sharp sand. With such a sill, 

 having the centre web below the rabbet which rests on the wall 

 and becomes embedded in the cement, any cross movement of the 

 sill upon the wall is prevented, and no anchor bolts are necessary. 



The iron frame of the superstructure, which is in general 

 similar to that already described, is bolted securely to this sill. 



The woodwork used upon these houses is of the same general 

 shape and detail as that already described, but is preferably of 

 clear white pine, in order that a higher finish may be obtained, as 

 cypress, no matter how carefully and smoothly it may be milled, 

 becomes woolly and rough by contact with moisture, and this 

 prevents its use in greenhouses where a permanent high finish is 

 desired. In curvilinear houses the iron rafters should be bent lo 

 fit the roof lines, and this bending, except in the case of a very 

 large radius being used, should be done while the iron is heated to 

 a proper and even temperature ; otherwise, its strength is greatly 

 impaired. Of course great care must be exercised in the heating 

 of iron for such bending, and ovens and other conveniences 

 especially designed for this purpose are necessary to prevent an 

 uneven heating or burning of the iron, which would be equally as 

 destructive to its strength as would the cold bending. 



Glazing. I will now pass to some important details in glass 

 houses, and first the glazing. The first thing necessary is to get 

 suitable glass. For roses, and other plants which require the 

 most perfect light, I would certainly recommend the use of 

 French or Belgian glass — that known generally as double thick, 

 second quality, the first quality being too expensive and not 

 possessing any material merit for plant culture other than that 

 possessed by the second quality. For other greenhouse purposes, 

 I believe glass of American manufacture is well suited, anrl have 

 no doubt that the time will soon arrive when we shall be able to 

 compete in quality, as in price, with glass of a foreign make. I 

 think that the only reason our domestic factories do not produce 



