FOREST UTILISATION 101 



ing it with antiseptic substances, such' as carbolineu'm, sulphate 

 of copper, corrosive sublimate, or creosote ' A-* a -;rule, 

 heavy woods are also durable, but Beech; which' 'quickly 

 decays on exposure to the weather, forms an exception. 



Heating power. There is at present no satisfactory measure 

 for testing heat-values. The calorimeter, which is used for 

 the purpose, is not of practical utility, for it does not take 

 sufficiently into account the quick development of heat by 

 coniferous woods compared to the slow, equal fire of Beech 

 wood burning with little smoke. 



Defects in Timber 



The more important of the fungoid diseases causing decay 

 in wood have already been mentioned. Of other defects, one 

 deserving notice, as affecting sound wood, is the reddening or 

 "false heartwood" of Beech. This discolouration in the 

 neighbourhood of a wound, very often at a broken branch, is 

 due to a change in the construction of the cells, and is an 

 effort to prevent the entrance of spore-containing water into 

 the tree. The timber is rendered unfit for many purposes. 



The blueness sometimes seen in summer on coniferous 

 timber that has lain long without drying sufficiently is caused 

 by a fungus, Ceratostoma piliferum. According to the most 

 recent investigations, it appears that this is only a blemish as 

 regards appearance, and that it does not in any way harm the 

 timber's strength, weight, or other qualities. 



Of defects occurring in sound wood, the following are 

 those of most consequence : 



Heart-shafy cracks, or rents proceeding from the pith 

 radially, are generally the result of rapid drying of the 

 timber. Frost-rib and frost-crack have been dealt with in 

 a previous paragraph under "frost." Ring-shake is a separa- 

 tion of the tissues along the line of an annual ring. It may 

 be caused by a sudden acceleration in the growth of a tree, 

 when, for instance, a Silver Fir which has long been kept 

 under shade is suddenly given full liberty of light. 



Abnormal direction of fibres. Common forms of this are 



