142 



Seasoning of Wood : Strength of Timber. 



574. Wood cut in planes radiating from the center can not warp. 

 "When sawn into this form, there is a waste from a feather-edge 

 on one side, and from extra thickness on the other, but the silver- 

 grain is brought out with great beauty in some species by this mode 

 of cutting, and for some uses it may be preferable. When wood 

 is to be used as the foundation for veneering, it should be cut as 

 near as may be in the direction of the medullary rays, and it must 

 be thoroughly seasoned. 



575. English shipwrights generally consider that three years are 

 required to season large timbers. They are usually cut to shape a 

 year before they are framed, and then left another year in the 

 skeleton before being planked. 1 All wood used in carving requires 

 the most careful and thorough seasoning. 



576. Hard-woods season more slowly than those of light open 

 grain. They may often be cut to nearly the shapes required for 

 use before being put away to dry, and should be piled open with spaces 

 for the air to circulate between the pieces. It may be desirable to 

 pile them over again, from time to time, so as to expose the parts at 

 first in contact. 



The Strength of Timber, ivith respect to its Form, and to the Lines of 



Growth. 



577. The strength of the timber when used in horizontal pieces 

 depends upon its form, and upon the manner in which it is cut, 

 with reference to the layers of annual growth. If laid flatwise, 



71. Proper Mode of placing a 

 Plank to scc-uro Durability 

 and Strength. 



72. Improper Mode of placing a Plank 

 to secure Durability and Strength. , 



Avith the layers convex on the upper side,' they act as an arch, and 

 tend to give it strength. If the same piece were laid edgewise, 

 like a joist, it would be much stronger than if the lines of growth 

 Avere transverse, and Avhen such pieces break from over-loading, the 

 crack is more apt to be between, than across, these layers of growth. 



l Britton on ihe Dry Rot, p. C8. 



