DEFECTS IN TIMBER AND GENEEA.L 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.^ 
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, 
^ Good flooring boards are often cut on the quarter, that is with the 
annual rings at right angles to their faces. 
