310 FORCING DEPARTMENT. 



MATERIALS BEST ADAPTED FOR HOT- 

 HOUSE ROOFS. 



Of what materials the construction of Hot-House 

 Roofs may most suitably be made, is a subject that 

 has occupied, of late, the anxious attention of many 

 horticulturists ; and various and conflicting have 

 their opinions been, insomuch that it would be a 

 matter of serious difficulty for a person to come to a 

 satisfactory conclusion which material bears the 

 preference. 



Let us commence ab-ovo. During the last half 

 century, the authors of all the numerous improve- 

 ments that have been adopted, in the formation, &c. 

 of these structures, have principally had in view 

 such inventions as would tend to admit the greatest 

 portion of sun and light to the trees or plants, in the 

 ungenial days of Winter and of Spring. Since it 

 has been generally acknowledged, and is now estab- 

 lished, that sun and light are amongst the first and 

 most essential requisites for early forcing, several 

 schemes have been resorted to, for their more unre- 

 strained admission ; such, for instance, as a reduc- 

 tion of the substance of materials in the wood 

 houses, to within half the size of what prevailed with 

 our antique forefathers, as also by the introduction of 

 metallic substances. 



It has, however, been stated by many, that the 

 latter materials are unfit for Hot-House Roofs ; as 



