172 On the Form of the Glass of a Forcing-house. 



and according to that maxim, I recommended the construction 

 referred to, as one likely to afford a greater quantity of fruit 

 in a given space, than any plan with which I am acquainted. 

 If I have been understood as having brought that plan into 

 notice, believing it to be the best possible, I shall be exceed- 

 ingly sorry. It is evidently not that which will receive the 

 greatest quantity of the sun's rays ; nor is any form hitherto 

 proposed, at least, as far as I know, calculated to attain that 

 object. 



In desiring, through you, to point out to the London Hor- 

 ticultural Society, what that figure is, which will receive the 

 greatest possible quantity of the sun's rays, at all times of the 

 day, and at all seasons of the year, I do not presume that any 

 of the members are ignorant of the solution of so simple a 

 problem. It is the supposed difficulty of constructing it, 

 which I am persuaded, has deterred many from bringing it 

 into notice. The difficulty not appearing by any means in- 

 surmountable, since the use of cast iron has become so fami- 

 liar, I have lately turned my attention to the subject; and 

 am happy to find that, in reality, there is no difficulty in the 

 case, even if the work was to be constructed in wood. 



The glass, in ordinary forcing-houses, is set in a plane at 

 right angles, or nearly so, to that of the meridian, and more 

 or less inclined to the horizon. It is, therefore, evident, that 

 the rays of the sun will fiill in a perpendicular direction on 

 this inclined plane (if it be not calculated to receive the rays 

 in that direction, at either solstice) only twice in the year, 

 and that for a very short time ; no longer than while the 

 sun is in the meridian, on two days in the year. At all other 

 times the rays fall in an inclined direction, and are never 



