Periodical Literature 117 



properties for the various species when plotted as ordinates with 

 the corresponding specific gravity as abscissae have shown in some 

 cases practically a straight line relation. In other cases the 

 strength increases more rapidly than does the specific gravity. 

 The most satisfactory form of equation for expressing the relation 

 for both green and air-dry material has been foimd to be that of 

 the parabola F^PG", where F = shrinkage or some mechanical 

 property. P = a constant: G^ = specific gravity based on oven- 

 dry weight and volimie as tested; m = power of curve." 



"The following properties gave approximately straight line 

 relations when plotted against specific gravity: 



Shrinkage: Volumetric, radial, tangential. 



Static bending: Fiber stress at elastic limit, modulus of rupture, 

 modulus of elasticity, work to elastic limit. 



Impact bending: Modulus of elasticity. 



Compression parallel to grain: Fiber stress at elastic limit, 

 crushing strength, modulus of elasticity. 



Shear parallel to grain : When siirface of failure is radial, when 

 surface of failure is tangential." 



"The following properties showed decided curves. The strength 

 or mechanical property increasing more rapidly than the specific 

 gravity : 



Static bending : Work to maximum load, total work. 



Impact bending: Fiber stress at elastic limit, work to elastic 

 limit, height of drop causing complete failure. 



Compression perpendicular to grain : Fiber stress at elastic limit. 



Hardness — load required to imbed a .444-inch ball to one-half 

 its diameter: End surface, radial surface, tangential surface. 



Cleavage strength per inch of width : When surface of failure is 

 radial, when surface of failure is tangential." 



Tension perpendicular to grain: When stirface of failure is 

 radial, when surface of failure is tangential." 



"While in most instances the various properties follow the 

 general relation quite closely^here are but few species which are 

 not exceptional in one or more properties. Not infrequently the 

 exceptional property of any species indicates the use to which it is 

 best adapted." 



S. J. R. 



Deductions from Strength Tests of Woods. By J. A. Newlin, American 

 Lumberman, Jan. 16, 1915, pp. 32-33. 



