DEFECTS IN TIMBER AND GEN REAL 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 pf 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 ovor the spot 

 where limbs or branches have decayed and fallen off. 



Straightness of Grain 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, ns it does not stand weathering like the heart- 

 wood and is generally the first to decay ; there should be 



