100 Description of a Forcing House for Grapes. 



and descriptions of such Forcing Houses, as theory and 

 practice prove to have been properly constructed for the 

 culture of every different species of fruit, were published by 

 the* Horticultural Society, much useful information might 

 be conveyed to the practical gardener. Under these im- 

 pressions I send the following description of a Vinery, in 

 which the most abundant crops of Grapes have been perfectly 

 ripened within less time, and with less expenditure of fuel, 

 than I have witnessed in any other instance. 



It is well known that the sun operates most powerfully in 

 the Forcing House, when its rays fall most perpendicularly 

 on the roof; because the quantity of light, that glances off 

 without entering the house, is proportionate to the degree of 

 obliquity with which it strikes upon the surface of the glass ; 

 and it is, therefore, important to every builder of a Forcing 

 House to know by what elevation of the roof, the greatest 

 quantity of light can be made to pass through it To ascertain 

 this point, I have made many experiments, and the result of 

 them has satisfied me that, in latitude 52°, the best elevation 

 is about that of 34 degrees ; and relative to that elevation the 

 position of the sun, in different parts of the year, will be nearly 

 as represented in the annexed sketch, which is taken from the 

 Vinery I have mentioned. Aoout the middle of May, the 

 elevation of the sun will nearly correspond with that of the 

 asterisk A, and in the beginning of June, and again early in 

 July, it will be vertical at B, and at Midsummer it will, at C, 

 be only six degrees from being vertical. The asterisk 1 > points 

 out its position at the equinoxes, and E its position in mid- 

 winter. 



In this building, which is forty feet long, and is heated 



