18 BULLETIN 67, U. S. DEPARTMENT OF AGRICULTURE. 
per cent greater and a crushing strength 18 per cent greater than the 
fire-killed lodgepole pine. It might seem at first sight that these 
differences were due to deterioration on the part of the fire-killed 
material, but an analysis of the values in regard to weight and a 
comparison with values obtained from other tests on lodgepole pine 
indicate that deterioration is not the probable cause of the difference. 
It has been proved conclusively that in any species the strength of the 
clear wood varies directly with its dry weight. 
