DURABILITY OF TIMBERS. 45 



durability : for instance, the wood of Douglas fir is described as 

 being " very durable " and darker in colour than those of 

 " pines," oak, and Robinia Pseud-acacia (commercially known 

 in this country as " acacia "), which are grouped together as 

 " durable." On the same page, it is frankly admitted that there 

 are exceptions to the rule, and that the woods of two cypresses, 

 holly and alder, are durable despite of their light colour. 



But what are the facts ? According to observations made in 

 French coal-mines (and related in Mathey's Exploitation 

 Cotnmerciale des Bois), the following represents the order of 

 durability of pit-props (beginning with the most and ending 

 with the least durable) made of different woods : (i) oak, (2) 

 Scots pine, (3) alder, (4) ash, (5) cluster pine, (6) Robinia 

 Fseud-acacia, (7) willow, (8) maple and sycamore, (9) elm, (10) 

 aspen, (11) cherry, (12) birch, (13) hornbeam, (14) beech, (15) 

 poplar (not aspen). Not perfectly in accord but mainly so were 

 the results obtained by R. Hartig with buried wood (heart-wood 

 or its equivalent). He found : [a) most durable, larch, Scots 

 pine and Robinia Fseud-acacia ; (b) less durable, oak and elm ; 



(c) still less durable, common silver fir and Norway spruce ; 



(d) least durable, lime, birch, beech and poplar. 



If we consider extra-European woods, some cases in opposi- 

 tion to the rule concerning depth of colour and durability are 

 notorious. Some dark woods are by no means durable ; for 

 instance karri, rivalling jarrah in depth of colour and resembling 

 it closely, is notoriously subject to fungal decay (popularly 

 termed "dry rot"). On the other hand, the very light-coloured 

 satinwood is extremely durable; I have myself seen satinwood 

 stairs out of doors in London that are still sound after forty 

 years of usage. 



In order to obtain evidence of an unbiassed nature, I analysed 

 the statistics given concerning the durability of Indian timbers 

 in Troup's Indian Forest Utilisation. Troup ranges Indian 

 woods into six classes according to their durabilities. Here I 

 give the main results of my analysis of his first two and last two 

 classes. In his class " extremely durable " are six woods, of 

 which four are dark brown or dark red, one (teak) is brown, 

 and the remaning one (Fagraea fragrans) is light coloured (light 

 brown). In the next class, " very durable," are eighteen woods, 

 of which six are certainly dark in colour, four are brown or 

 reddish-brown (oak to mahogany in colour), one is light red 



