144 



PROPERTIES OF WOOD. 



usual to find both sound and unsound internal sapwood in the 

 same zones. 



Nanquette states that it is difficult to detect by mere inspec- 

 tions sound internal sapwood in oaken staves, as when the 

 wood is long exposed to the sun and air its tint becomes 

 indistinguishable from that of normal heartwood ; it may, 

 however, be detected readily by pouring water on the wood. 

 Internal sapwood is as perishable as ordinary sapwood and 

 soon decays in beams, and in planks gets wormeaten. Mathey 

 says that much parquet flooring near Lyons containing 

 internal sapwood has been attacked by Lyctus canicidattis. 



Wood containing 

 internal sapwood 

 when used for 

 staves renders 

 them brittle, so 

 that casks thus 

 made are not 

 strong and give 

 a mouldy taste 

 to wine. 



This defect 

 occurs in all 

 kinds of oak- 

 wood, according 

 to Mathey; it is 



Fig. 61. Beechwood injured by fire. (After Boppe.) 



commonest in the wood of sessile oak, being rarer in that of 

 pedunculate oak, while Quercus tardissima (chene dc Jain], 

 which may be named the June oak, appears to be exempt 

 from internal sapwood. 



Burned "Wood. The cambium of standing trees may be 

 killed by fire or by the sun, the latter causing sun-blister, or 

 bark-scorching, which is described in Vol. IV. Fig. 61 shows 

 a section of beechwood injured by fire. Beech and ash are 

 specially liable to this form of injury owing to fires made by 

 wood-cutters, but also frequently Scots-pine trees are rendered 

 unsound at their bases by ordinary forest fires. Such wood 

 is useless except as firewood. Tr.] 



Wood with red or brown streaks is not uncommon in spruce 



