BULLETIN 286, TJ. S. DEPARTMENT OF AGRICULTURE. 



LONGLEAF PINE. 



Steamed for 6 hours at 30 pounds pressure; vacuum of 26 inches applied for 1 hour; 

 cylinder filled with creosote and pressure of 128 pounds applied for 5£ hours at a 

 temperature of 140° F. Absorption, 12| pounds per cubic foot of wood. 



DOUGLAS FIR. 1 



Boiling process. — Boiled in creosote for 21| hours at temperature of 215° F.; 2 loss of 

 moisture during boiling, 1.2 pounds per cubic foot of wood; pressure raised from to 

 145 pounds per square inch in 5| hours; temperature about 190° F. Absorption of 

 oil, 11.2 pounds per cubic foot of wood, as determined by measuring tank readings. 



Steaming process. — Steamed at 90 pounds pressure per square inch for 4 1 hours; 

 temperature about 325° F.; vacuum of 20 inches applied for 18£ hours; temperature 

 220° F. at end of period ; cylinder filled with oil and pressure raised from to maximum 

 pressure of 140 pounds per square inch; pressure period, 2\ hours; temperature of the 

 oil, about 208° F. Absorption, 3.1 pounds per cubic foot of wood, as figured from 

 increase in original weight of stringers. The stringers were not weighed after steam- 

 ing, so that the probable loss can not be taken into account in computing the absorption. 



METHOD OF TESTING. 



The stringers were tested in bending by supporting them at the 

 ends and applying the load at two points located one-third of the 

 span from each of the end supports. This system corresponds 

 closely to conditions of practice. In testing the beams the load was 

 applied gradually and a record kept of the deflections corresponding 

 to regular load increments. Four factors were calculated from the 

 data derived from each bending test, all in terms of pounds per 

 square inch: 



FIBER STRESS AT ELASTIC LIMIT. 



This is the greatest stress that can occur in a beam loaded with 

 an external load from which it will recover without permanent 

 deflection. 



MODULUS OF RUPTURE. 



This is the greatest computed stress in a beam under a breaking 

 load. 



MODULUS OF ELASTICITY. 



This is a factor computed from the relation between load and 

 deflection within the elastic limit, and represents the stiffness of the 

 wood. 



LONGITUDINAL SHEAR. 



This is the stress tending to split the beam lengthwise along its 

 neutral plane 3 when under maximum load. 



> Run made Mar. 5, 1908. 



2 Some timo after the treatments were mado it was reported by the treating-plant officials i hal t he ther- 

 mometer grvin ding registered 40° F. too low. 



3 Plane between upper and lower halves when beam is horizontal. 



