DEFECTS IN TIMBER AND GENEliAIi NOTES 293 
and spruce, branch close to ground level, and the branches 
are very close to one another ; hence the great number of 
knots, although usually of small sizes, to be found in 
the spruce or white deal ; hence also the reason why they 
cannot be avoided even in the smaller scantlings of that 
class of timber. 
Knots in pine panelling, though they do not add to the 
quality of the timber, certainly add to its attractiveness, 
giving variety of grain and colour, particularly noticeable 
on stained or varnished surfaces. 
Dead knots are caused by timber growing over the spot 
where limbs or branches have decayed and fallen off. 
Straightness of G-rain is a necessity in some situations. 
There are very strong timbers, some of the strongest, which 
have a twisted or crooked grain, but in the conifera tribe, 
where in the longitudinal direction the natural trend of the 
grain is straight, it is dangerous for certain purposes to use 
timber when the grain pursues a diagonal or slanting direc- 
tion ; it rarely does so, and it might not be of much conse- 
quence in a beam if laid the proper way ; but for vertical 
loads or pile-driving it is very objectionable, as in this case 
there is a risk of its shearing off when subjected to heavy 
loads or to severe hammering. 
Sap is the great bane of the timber selector. The ques- 
tion as to what is really sap and of the amount of sap 
allowable in constructional timber is a very knotty one, it 
causes a good deal of friction, and often leads to lawsuits 
and arbitration. 
It is practically impossible to get timber of large sizes 
without sap. Oregon is the only timber much used which 
may be said to be free of it, and specifications are often 
misleading. Sapwood on fir and pine timber is undoubtedly 
objectionable, as it does not stand weathering like the heart- 
wood and is generally the first to decay ; there should be 
