Suggestions for a Plan for Forcing-houses. 351 



The objections to the proportions, which are given in the 

 Transactions of this Society, are, that the house would be 

 much too high relative to its width and length ; that the too 

 close approximation of the bars at the top would give too 

 much shade, and that the vapour condensed into water 

 would necessarily drop upon, and injure the fruits and 

 plants, owing to the want of sufficient declivity in the upper 

 part of the roof ; there is, I also think, a large portion of the 

 glass, towards the bottom of the house, which stands much 

 too nearly upright. But the whole of these defects may be 

 readily removed by employing a small segment of a much 

 larger sphere, as Sir George Stuart Mackenzie has 

 suggested : and as low and as wide a forcing-house, as can 

 be wanted for almost any purpose, may be readily obtained. 

 Instead of the half of a hemisphere of thirty feet diameter, 

 let the half of one of fifty feet be chosen, and from the base 

 of this cut off thirty-five degrees, and from the summit fif- 

 teen degrees, as represented in the annexed sketch ; and the 

 following proportions for a forcing-house will be given. Its 

 height, including eighteen inches of brick work, will be 

 twelve feet ; its width in the centre, fourteen feet ; and its 

 length very nearly forty feet : and there are very few pur- 

 poses for which a house constructed according to some of the 

 intermediate forms, between that above-mentioned, and the 

 half hemisphere, will not be found extremely well adapted ; 

 as a front walk, where wanted, may be sunk beneath the level 

 of the soil, or the brick wall may be made higher. 



The injurious effects to be apprehended from the approxi- 

 mation of too numerous bars, may be easily obviated by 

 uniting two into one, as represented in Fig. 2 ; and the bars 



