SPECIFIC WEIGHT. 61 



deeper the colour, the heavier the wood. It is very difficult to 

 decide how far the sp. weight is thus affected, as individual 

 variations and the natural falling off in weight from the inner 

 zones of the wood outwards complicate the question. Hartig 

 states that the colouring matter in oakwood raises its dry 

 weight 6 per cent. Woods, the cell-lumina of which are 

 filled with colouring matter, such as tropical dye-woods and 

 artificially injected wood, are considerably heavier than light- 

 coloured wood.* 



(9) Resin increases the weight of conifers. According to 

 Mayr,t when sap wood passes into heartwood there is a gradual 

 change from liquid turpentine into solid, heavy rosin. It is 

 not true that new formations of resin occur in old wood 

 parts. The absolute quantity of it remains constant ; only its 

 form alters ; the turpentine becomes oxidised and concentrated 

 only. The increase in weight is greatest in species that con- 

 tain the most turpentine, #.//., Weymouth pine, Scots pine, 

 spruce, and, least of all, silver-fir. The stump is heaviest, not 

 only because its wood has thick walls, but because it contains 

 the most resin. When resin formation begins (ride " Defects 

 in Wood"), and the cell-walls dry, a very remarkable increase 

 in weight follows uvsin-galls, hard kno! 



(10) Abnormal tissues in woods usually increase their 

 weight, but their strength is thus greatly injured. Occluded 

 woods, burrs or excresei'iices in wood, and contorted fibres are 

 usually heavier, but not therefore better than normal wood. 

 Among these may be reckoned the abnormally hard wood 

 which all our conifers produce on the lower side of branches, 

 at bends in the stem, on the rootstock, and on the eastern side 

 of stems, that woodmen name hard, or red, wood (cf. " Defects 

 in Wood"). 



(11) Organic and inorganic salts, that are partly soluble in 

 water, contribute appreciably in the formation of sapwood. 

 Such are sugar, albumen, gums, etc. In heartwood they have 

 no sensible influence on the weight of wood. Floating wood 



* [The black wood of ebony weighs 75 80 Ibs., ami its sapwood only 

 49 50 Ibs., per cubic foot, the extra weight being due to a coloured substance 

 that fills the luniina till the structure is scarcely discernible by a micro- 

 scope. Tr.] 



t H, Mayr, " Das Holz der Nadelholzer." 1894. 



