4 



BULLETIN 77, U. S. DEPARTMENT OF AGRICULTUKE. 



graphically in figures 1 and 2. The increase in strength of the props 

 due to seasoning is very evident in each species, and the average 

 strength of the seasoned props of all species is 2.3 times that of the 

 green ones at both maximum load and elastic limit. In the case of 

 the caps the average strength of the dry timbers at the maximum 

 load is 1.6 and at elastic limit 2.2 times the strength of the green 

 timbers. While at the elastic limit the influence of the moisture 



SSAIR WYi 



A'R DRY , . Z 



-AW P»VSS 



GREEN 



S'GREEN 



9232^ 



■^AIR DRY.^ 



mm 



mSum 



>^AIR DRY 



SS 84083 





?5308l 



JS242M 



AIR DRY- , 



_GREEjr 



■S4I39 



1MI 



AIR DRY ' -■ ' ■ ' : ■ . ' ■ - 



■J7340SI 



OREEH 



S^'AIR DRY 



' "^4768 1 



PM^«DI«S! ! 



QREEN ■ ' :...,..:.. .46971 



^69543 



O0U0LAS FIR 



L0DOEP0LE PINE 

 SHIPMENT -A- 



BRISTLE-CONE PINE 



ENGELMANN SPRUCE 



WESTERN YELLOW PINE 

 SHIPMENT -A- 



ALPINE FIR 



L0D0EP0LE PINE 

 SHIPMENT -B- 



WESTERN YELLOW PINE 

 SHIPMENT -B- 



MOO 2000 3000 4000 5000 6000 7000 8000 9000 



MODULUS OF RUPTURE - POUNDS PER SQUARE INCH 



Fig. 2.— Comparison of different species; 6-inch round mine caps— air-dried and green. 



was practically the same for both the crushing and bending tests, at 

 the maximum load it is much more pronounced in the crushing tests. 

 Stiffness in bending was increased by seasoning to 1.4 times the 

 green value. There appears to be no marked variation in this 

 strength ratio among the various species tested. It is slightly below 

 the average in Douglas fir, due to the consistently high values for 

 the green material in comparison with the other species, 



