DEFECTS IN TIMBER AND GENERAL NOTES 297 



and occasional bad ends ; pitch pine is remarkably free from 

 them, and Baltic redwood has probably less defects than 

 any timber in the market and causes but little loss in 

 cutting up, and one seldom opens a log of either of these 

 timbers and finds defects inside which were not noticeable 

 on the sides or ends. 



In planks cut from the centre of a log there is a risk of 

 the centre portion lifting up, and when used for flooring 

 the annual rings should have the convex side uppermost ; 

 the part nearest the pith should be put downwards as per 

 Fig. 52 and not as shown in Fig. 53. l 



Toughness is a familiar but indefinite term ; most of the 

 flexible woods are often called tough, but a tough wood should 

 be both strong and pliable, as are hickory, elm, or ash. 

 Tough wood is required where loads are applied in the form 

 of blows and shocks, as for instance in the spokes of a cart 

 wheel, which are subjected to sudden jars or shocks when- 

 ever the wheel passes over a stone, and these jars and shocks 

 are much more severe than is generally supposed. Willow 

 and bamboo are called tough, but would not be suitable for 

 such a purpose as this, and willow is only tough when 

 wet. 



Flexibility is the term applied to timber which will stand 

 considerable deformation before rupture, as for instance 

 bamboo, lancewood, or willow, but these would not be suit- 

 able to carry permanent loads. In Indian architecture, 

 where bamboo is used, it is always given a convex curve. 



Of late years a good deal has been done in the way of 

 illustrating different timber by microscopical or enlarged 

 sections, to which photography has lent its aid. To 

 Nordlinger on the Continent, E. B. Hough in America, 

 Herbert Stone and James A. Weale in this country, 



1 Good flooring hoards are often cut on the quarter, that is with the 

 annual lings at right angles to their faces. 



