110 ORGANIC STRUCTURE. 



contained? It is said that if Brazil wood be deprived 

 of its colour by any solvent, it loses also its strength 

 and ponderosity. In the case of fir timber, it is 

 very evident that its durability is entirely owing 

 to the resinous and slowly exhalable quality of the 

 sap. Many kinds of timber, as beech, for instance, if 

 kept constantly under water, so that its natural sap 

 be not dissipated, will last for many years. Ash, 

 when arrived at maturity, is as tough under pressure, 

 and solid under the tool as the oak; but it decays 

 much sooner in the air ; the durability of the latter 

 must therefore depend on some inherent quality not 

 possessed by the former. Now as the oak contains 

 an extraordinary quantity of an astringent principle, 

 may not this be the preservative matter ? On this 

 point an inquiry should be instituted, whether that 

 scantling of oak containing the greatest share of this 

 astringency be or be not more durable than a similar 

 scantling containing less. Another inquiry should be 

 made ; whether one description of soil produces oak 

 timber of superior quality as to durability than 

 another, and what is the difference of these soils. It 

 is well known that the most stately oaks grow on 

 deep loam reposing on a clayey subsoil ; but the 

 durability of the timber, and the constituents of the 

 soil, have not been, perhaps, sufficiently compared. 

 Some soils are bland and composed of simple earths ; 

 others, viz. clays, loams, and gravels, are strongly 

 impregnated with ferruginous qualities, which may 



