Bui. 607. U. S. Dept. of Agriculture 



Plate IX. 



Penetrance Specimens. 



Specimens arranged in order of treatment as given in Table 16. Group No. 1 treated with creosote. 

 Time of treatment, 2 hours; pressure, 75 pounds per square inch; temperature, 180° F. Group 

 No. 2 treated with 80 per cent creosote, 20 per cent tar. Time of treatment varied; temperature, 

 180° F. Group No. 3 treated with 6(i| per cent creosote, 33J per cent tar. Time of treatment varied; 

 temperature, 180° F. Group No. 4 treated with 80 per cent creosote, 20 per cent tar. Pressure 

 varied; temperature, 180° F. Group No. 5 treated with 66§ per cent creosote, 33$ per cent tar. 

 Pressure varied; temperature, 180° F. 



