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XXVI. Upon the Advantages and Disadvantages of curvili- 

 near Iron Roofs to Hot-houses. In a Letter to the Secre- 

 tary. By Thomas Andrew Knight, Esq. F. R. S. $c. 

 President. 



Read October 1st, 1822. 

 My dear Sir, 



You have more than once expressed a wish to receive from 

 me an account of my opinion of the comparative advantages 

 and disadvantages of the iron curvilinear, and common hot- 

 house roofs of sliding lights, in the culture of the Pine Apple, 

 as soon as experience should have enabled me to give it. 

 I am now, I believe, in possession of sufficient information 

 to enable me to give an opinion, with some degree of confi- 

 dence, having had the experience of three summers, in 

 which I have nearly sacrificed more than two hundred very 

 fine fruiting Pine Apple plants in my curvilinear roofed hot- 

 house. I have, however, ultimately succeeded to the full 

 extent of my hopes and expectations, and I give a decided 

 preference to the curvilinear roof. I must nevertheless 

 admit, that it has some defects, which I shall endeavour to 

 point out, and set in opposition to its perfections. 



The curvilinear iron roof certainly transmits heat more 

 rapidly than one of wood of the ordinary construction, but 

 not to any considerable extent, I think, more rapidly than a 

 roof composed of wood and glass would do, if the wood were 

 employed in as small quantities as the iron is, and not nearly 

 to as great an extent as a roof composed wholly of glass would 

 do, if such could be constructed. 



