8 BULLETIN" 676, U. S. DEPARTMENT OP AGRICULTTTRE. 



the equation values and another "species-locality" fall far below 

 them. 



In figure 5 are plotted the curves of the equation for modulus of 

 rupture in static bending in green material, M = 18500 Vg^ and of 

 the equation for the same property in air-dry material, M = 26200 ^g^! 

 In order to give a graphical idea as to the reliability of these 

 equations, the specific gravity and the modulus of rupture of each 

 ''species-locality" have been plotted as a point. The reference num- 

 ber placed near each plotted point is assigned to the "species-locality" 

 in the order of its respective specfic gravity as determined from 

 compression parallel to grain specimens of green wood. In figures 

 6, 7, and 8 the data are given for the curves on shrinkage in volume 

 from green to oven-dry condition, maximum crushing strength in 

 compression parallel to grain, and fiber strength at elastic limit in 

 compression perpendicular to grain. 



Under each property is listed in this second portion of Table 1, for 

 both green and air-dry conditions, those percentages of the equation 

 value above which were one-tenth of the "species-localities." Simi- 

 larly, there are listed those percentages above which were one-fourth 

 of the "species-localities," those below which were one-fourth, and 

 those below which were one-tenth. For instance, in static bending 

 (green), one-tenth of the "species-localities" tested had a modulus of 

 rupture of more than 114 per cent of what the specific gravity equation 

 indicated they should have had; one-fourth of them had a modulus of 

 rupture greater than 108 per cent of the equation value; one-fourth 

 of them less than 91 per cent of the equation value; and the lowest 

 one-tenth had a modulus of rupture less than 84 per cent of what the 

 equation indicated they should have had. It follows from these 

 figures that one-half of the "species-localities" had a modulus of 

 rupture of betv/een 91 per cent and 108 per cent of the value given by 

 the equation, and that the other one-half were evenly divided between 

 those that were more than 108 per cent and those that were less than 

 91 per cent. 



The third portion of Table 1 gives the actual value of each property 

 for each "species-locality" as determined by the tests, expressed as a 

 percentage of the value computed from the specific gravity by the 

 use of the equation at the head of the column. For instance, it is 

 found from the table that air-dry Biltmore ash has a modulus of 

 rupture 98 per cent as great as that of the average wood of its specific 

 gravity, the modulus of rupture of the average wood of this specific 

 gravity being the figure given by the equation. These percentages are 

 given for both green and air-dry wood. 



