CONSTRUCTION AND HEATING OF GLASS HOUSES. 65 



bench to the wood siding and thus causing early decay at such 

 connections. 



For the connecting of the rafters, giving longitudinal stability to 

 the roof, and for the support of the glazing bars, two inch by one 

 and one-fourth inch by one-fourth inch angle iron purlins are used. 

 This size of iron is selected, as the two-inch web gives the 

 necessary strength, and the one and one-fourth inch gives sufficient 

 surface for the attachment of the roof bars by means of small 

 screws, yet throws but little shade. These purlins are spaced 

 according to the length of the rafters, and the size of the glazing- 

 bars in use, the upper one being so placed as to afford support for 

 the upper ends of the glazing bars, they all resting on the purlin 

 about one-fourth to three-eighths of an inch, and being toe-nailed 

 to the cypress header which is screwed on the purlin. 



The ends of the house are braced with one, two, or three lines 

 of purlins, according to the width and shape of the house. Iron 

 doorposts fastened to cast iron bases in the same manner as the 

 side posts, run up to the rafter and are tied together by a cast 

 iron doorsill at the bottom. The end purlins just mentioned run 

 from the end posts and rafters to the doorposts, thus forming a 

 very stiff end, and one to which the necessary light woodwork is 

 easily attached. 



We now come to the last part of the iron frame, but I think one 

 of the most important, namely the gutters. The gutters should 

 be of iron, but even that would be of no advantage unless we 

 could prevent their contents from being frozen, for, as we all 

 know, in the process of freezing expansion takes place, which is 

 liable to burst or crack the gutters. I show here, however, a non- 

 freezeable gutter, of cast iron. It is so arranged that a small 

 portion of the inner warmth of the house is conducted to the 

 contents of the gutter, and thus prevents their being frozen. 

 These gutters are in use very largely throughout the country, and 

 I have never known in a single instance of their contents becoming 

 frozen sufficiently to prevent a fi'ee flow of water. I have, in 

 very low temperatures, ranging from zero downward, seen the 

 outer surface of the gutter coated with ice, but the warm side is 

 at all times free. This is a very important feature. First, it is 

 a permanent portion of the house, whereas the old wooden gutter 

 was the first part to rot and communicate decay to all its surround- 

 ing parts. Second, it prevents the possibility of ice forming 

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