190 Transactiom. — Misceltaneotis. 



Art. XVIII. — On a means of selecting the most durable Timber. 



By John Buchanan. 

 [Read before the Wellington Philosophical Society, 21st September, 1877.] 

 The purpose of the present paper is to explain a method by which timber 

 of the greatest utility, from trees of any species, may be determined. 



In the selection of timber for constructive purposes the only guide 

 hitherto has been the prevailing vague opinion that the timber of certain 

 trees is durable ; experience, however, has often proved that failures take 

 place with some of those species most highly valued, such as totara, 

 ( Podocarjms totara). In all such cases the failure has probably resulted from 

 that indiscriminate system which prevails of cutting down every tree within 

 reach, including young immature trees and quickly-grown mature trees on 

 rich alluvial bottoms, which always produce an inferior timber ; the use of 

 such inferior timber in wharves, piles of all kinds, or fence stuff, can only 

 result in premature decay. 



As a means to enable engineers to determine the value of any timber 

 I propose the adoption of a standard test of w^eiglit, based on an average 

 weight determined from at least twenty measured cube specimens of each 

 species, the specimens to be well seasoned, procured from different districts, 

 and grown under different conditions of growth. By comparing specimens 

 of the same cubic bulk of any timber with its own standard, the most durable 

 of that kind may be selected ; as it may be accepted as an axiom in the 

 physiology of timber, that the best wiU possess the closest structure, contain 

 the largest amount of secretions, and consequently will prove the heaviest 

 and most durable. 



If, however, our New Zealand timbers in their natural state, and selected 

 by the test of weight, do not come up in durability to the necessary require- 

 ments, there is still in reserve the auxiliary means used in other countries, 

 by which inferior timber is made durable, such as charring, or by the infusion 

 of antiseptic fluids into their structure, and it is possible the colony may ere 

 long waken up to the fact that the introduction of such preservatives has 

 been already too long delayed. 



