174 On the Form of the Glass of a Forcing-house, 



and useless expense to bring each pane of glass into the 

 form of a small segment of a sphere, it is evident that we 

 must be contented with a polygon. But the deviation from 

 the curve, in the size which I am about to recommend, is so 

 small, as will scarcely be perceptible. All this might be 

 easily demonstrated ; but the matter is so simple, that every 

 one, who considers for a moment the path described by the 

 sun, must be satisfied of the truth. I therefore proceed to 

 the mechanical part of the problem, and to point out the me- 

 thod by which the semi-dome may be constructed ; and in 

 doing so, any disadvantage attending it, will come into view. 



It will also have occurred to you, that there is a limit 

 prescribed to the size of a house, glazed according to this 

 figure, both by utility and convenience. A radius of fifteen 

 feet appears to me best suited to a house of this form. Any 

 thing less than this would be confined, and any thing greater 

 would render necessary an inconvenient height. Should it 

 be desired to make the length of the house more than thirty 

 feet, a spheroidal form may be resorted to with advantage. 

 But as that form would require a much greater degree of 

 nicety in the workmanship, a smaller segment of a sphere 

 may appear preferable. 



On looking at the elevation, Fig. 1, I doubt not of your 

 being struck with the neatness, I may say elegance, with 

 which this construction is capable of being arranged. For 

 my own part, I consider that several houses of this size and 

 form, disposed over a garden, would have a much better 

 effect than one great range. Whatever construction may 

 be adopted, it appears to me better, in many points of view, 

 to have several houses of a moderate size, than a long single 



