16 THE FORCING GARDEN. 



and additional influence upon everything exposed to 

 it, when wet or damp more than when it is dry. The 

 practical man will know at once how to appreciate the 

 double glazing above the single, on account of the 

 under glazing being preserved dry, which no single 

 method can do. 



Single glazing may be employed for all cool 

 orchard houses, vineries, cool plant houses, &c. ; but 

 I recommend all forcing houses and tender exotic 

 plant houses to be double-glazed on one of the plans 

 illustrated and described in this work. 



