50 TIMBER. 



For instance, of a piece of dry hickory (H. alba) we may expect — 



Strength in shearing pounds . . 1 , 200 



Strength in tension do 25, 000 



Distortion in tension per cent . . 2. 03 



Distortion i n compression do 1. 55 



Total distortion do 3. 58 



PRACTICAL CONCLUSIONS. 



From the foregoing considerations a few valuable facts, mostly famil- 

 iar to the thoughtful woodworker, may be deduced: 



In framing, where light and stiff timber is wanted, the conifers 

 excel; where heavy but steady loads are to be supported, the heavier 

 conifers, hard pine, spruce, Douglas spruce, etc., answer as well as 

 hard woods, which are costlier and heavier for the same amount of stiff- 

 ness. On the other hand, if small dimensions must be used, and espe- 

 cially if moving loads are to be sustained, hard woods are safest, and 

 in all cases where the load is applied in form of "shocks" or jars, only 

 the tougher hard woods should be employed. The heavier wood sur- 

 passes the lighter of the same species in all kinds of strength, so that 

 the weight of dry wood and the structural features indicative of weight 

 may be used as safe signs in selecting timber for strength. 



In shaping wood it is better, though more wasteful, to split than to 

 saw, because it insures straight grain and enables a more perfect sea 

 soning. 



For sawed stock the method of "rift" or "quarter" sawing, which has 

 so rapidly gained favor during the last decade, deserves every encour- 

 agement. It permits of better selection and of more advantageous 

 disposition of the wood; rift-sawed lumber is stronger, wears better, 

 seasons well, and is least subject to " working" or warping. 



All hardwood material which checks or warps badly daring seasoning 

 should be reduced to the smallest practicable size before drying, to 

 avoid the injuries involved in this process; and wood once seasoned 

 should never again be exposed to the weather, since all injuries due to 

 seasoning are thereby aggravated. Seasoning increases the strength 

 of wood in every respect, and it is therefore of great importance to pro- 

 tect wooden structures, bearing heavy weights, against moisture. 



Knots, like crossgrain and other defects, reduce the strength of 

 timber. Where choice exists, the knotty side of the joist should be 

 placed uppermost, i. e., should be used in compression. 



Season checks in timber are always a source of weakness; they are 

 more injurious on the vertical than on the horizontal faees of a stringer 

 or joist, and their effect continues even when they have closed up, as 

 many do, and are no longer visible. 



Rafted timber, Mln-dried or steamed lumber are, as far as our present 

 knowledge extends, as strong as other kinds, and wherever any of these 



