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XVII. A DESCRIPTION OF A FORCING-HOUSE FOR GRAPES; WITH 

 OBSERVATIONS ON THE BEST METHOD OF CONSTRUCTING HOUSES 

 FOR OTHER FRUITS. 



[Read before the HORTICULTURAL SOCIETY, May 3rd, 1808.] 



So much difference of opinion prevails amongst gardeners respecting 

 the proper forms of forcing-houses that two are rarely constructed quite 

 alike, though intended for the same purposes ; and every gardener is 

 prepared to contend that the form he prefers is the best, and to appeal 

 to the test of succcessful experiment in support of his opinion. And this 

 he is generally enabled in some degree to do, because plants, when 

 properly supplied with food and water and heat, will succeed in houses 

 the forms of which are very defective ; and proper attention is not often 

 paid by the gardener when his prejudices satisfy him that his labours 

 cannot be successful. It is, however, sufficiently evident, that when the 

 same fruit is to be ripened in the same climate and season of the year, 

 one peculiar form must be superior to every other ; and that in our 

 climate, where sunshine and natural heat do not abound, that form, 

 which admits the greatest quantity of light through the least breadth of 

 glass, and which affords the greatest regular heat with the least expendi- 

 ture of fuel, must generally be the best ; and, if the truth of this position 

 be admitted, it will be very easy to prove that few of our forcing-houses 

 are at present even moderately well constructed. I therefore think that 

 if plans 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 

 impressions 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 propor- 

 tionate 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 



