THE FORCING GARDEN. 



519 



of wood, if done in a neat and proper manner, have been found 

 to admit light sufficient to produce fruit as good as any that 

 has hitherto been produced in metalhc ones, without the dan- 

 ger attending the attraction of electrical matter, or their con- 

 ducting an immoderate degree of heat or cold, either of which 

 is extremely injurious to vegetation. A sufficient time has not 

 yet elapsed to prove their durability to be more than that of 

 good timber, which only should be used in erections exposed 

 to the vicissitudes of heat and cold, wet and dry ; but if we 

 may judge from metallic matter being used in sky-lights, and 

 other open situations, exposed to the same atmosphere, and 

 governed by the same laws, we should decide that wooden 

 houses, if properly constructed and kept in repair, will last as 

 long as metallic ones, if kept equally well. Iron is not in- 

 corruptible, and it is much to be questioned, that were it placed 

 in the same situation, whether it would remain in a state of 

 preservation much longer than many kinds of wood. Nails 

 are sometimes found quite decayed in old buildings, while the 

 timber, in which they are driven, is almost as fresh as when 

 first put up. Lignum vitae, as well as ebony, is so durable, 

 that scarcely any traces of decay have been discovered in either. 

 Box is very rarely found in a state of decay. It was a com- 

 mon opinion in the days of Pliny, that box, ebony, Cyprus, and 

 cedar, were indestructible. The great durability of these woods 

 arises, no doubt, from their texture, being very heavy and 

 close-grained ; water cannot be absorbed by them in any quan- 

 tity, they not being sufficiently porous. We have woods in 

 another class which are very durable, such as mahogany, 

 cedar, yew, teak, acacia, and some species of pines, &c. These 

 woods are of an open grain and very porous, but then, they 

 contain a quantity of oleaginous or resinous matter, which 

 occupies all their cavities, and therefore prevents the insinua- 

 tion of any moisture. Pliny, in his Nat. His. lib. 16. c. 40, 

 says, that the Temple of Apollo, at Uttica, the timber of which 

 vvas Numidian cedar, is said to have stood 1188 years. The 

 roof of Westminster Hall is of oak, and has stood undecayed 

 during a period of many centuries. 



The horizontal Cyprus, Cupressus horizontalis, a native ot 

 the Levant, is said to resist putrefaction, and to last for many 



