52 



ON THE MERITS OF IRON AND WOOD FOR ROOFS. 



the deficiency of the moisture exhaled by the powerful action 

 of the sun. 



Another important circumstance is worthy the gardener's 

 attention, namely, that iron houses should be painted internally 

 either annually or biennially at the furthest to prevent the drip 

 from the corroded iron injuring the foliage of the plants, for 

 I have always found this ochreous and metallic deposit injurious 

 to the leaves. 



Since these remarks were made, I have had subsequent proof 

 of the correctness of my former comparisons having extended 

 my observations still further in the year 1831, and these, as you 

 will perceive, fully confirm the accuracy of my previous calcu- 

 lations by working two houses at -the same temperature, 55 to 60 

 of Franheit, the result was as follows, the wood roofed house 

 consumed only a bushel and a half of coals every night, while 

 the iron house burnt from two bushels and three quarters ; to 

 three bushels ; this last experiment was two months later in the 

 season than when my attention was made directed to the subject 

 before, you will yet perpceive they bear the same proportions, 

 as to fuel, &c. as the former. 



The dimensions of the houses were as follows, the wood 

 roofed, fifty feet long, fifteen feet wide, and fourteen feet high ; 

 the iron roofed fifty feet long, thirteen feet wide, and twelve feet 

 high ; the latter was a vinery and had a pit in it for the culture of 

 pines, which very much reduced the cubic feet of air to be heat- 

 ed, as compared with the wood roofed house for the culture of 

 peaches which had no pit in the centre. Notwithstanding that, 

 however, the whole of my observations and calculations are un- 

 favourable to iron roofs, yet I am willing to admit that for light- 

 ness and neatness of appearance in the structure, iron has, and 

 always will have the advantage, but still I am confident that if 

 proper attention were paid to the construction of hothouses, and 

 to materials used in the erections the appearanee of a wood 

 roofed house would not be altogether objectionable. 



For assistingpersons building houses for horticultural purposes, 

 who may have had less practical experience than myself, I shall 

 here give a brief description of such materials and mode of con- 

 struction, which I think will combine the whole of the desired 

 objects. The first thing to be attended to is to give the roof a 

 proper pitch or inclination, so as effectually to carry off the watei 



