PENETRATION AND DECAY 379 



decay; and in this group in the sample from the 26-year old line (Fig. 7) 

 decay developed in only 6, or 8.1 per cent, of the poles. Moreover, 

 none of these decaying poles at the 26-year age had deteriorated far 

 enough to require removal. 



There is no evidence in the data warranting discrimination against 

 thin sapwood poles because of possible extra decay hazard. The 

 average sapwood thickness for all the inspected poles with penetration 

 less than 2.5 inches was 2.52 inches, and the average sapwood thickness 

 for the poles that failed was 3.19 inches. Only 34 per cent, on the 

 average, of the sapwood thickness was penetrated in the poles that 

 failed. When the distribution of the sapwood thicknesses of all the 

 poles with penetration less than 2.5 inches, and the distribution of the 

 sapwood thicknesses of the poles that failed, are plotted as in Fig. 9 

 there is a clear indication that serious interior decay is more likely 

 to occur in the poorly treated thicker sapwood poles than in the thinner 

 sapwood poles. 



The results of the study of actual conditions in line provide a means 

 for evaluating the practical effect of the current specifications for 

 creosoting southern pine poles. The purpose of the specifications is 

 to keep the number of well penetrated poles as high as commercial 

 production will permit, and to eliminate practically all of the poorly 

 penetrated poles at the source of supply. The hazard of failure by 

 decay in poles produced under the specifications appears to be reduced 

 to an economic minimum. 



