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BELL SYSTEM TECHNICAL JOURNAL 



pole, the suspected region was explored with an increment borer. 

 This tool, which is shown in Fig. 2, is designed to remove a core of 

 wood 0.2 inch in diameter. The increment borer cores were examined 

 to determine the condition of the wood. The depth of penetration of 

 the creosote, the thickness of sapwood, or the thickness of sound 

 shell overlying the decay, were measured on each core if there was any 

 internal decay present. In each decaying pole the shallowest pene- 

 tration was recorded. Knots, knot holes and woodpecker holes, scars 

 and other surface irregularities or injuries were examined to determine 

 their possible association with the internal decay. If the pole was 

 sound, a single increment borer core was taken at about 4.5 feet from 

 the ground for measurement of penetration and thickness of sapwood. 



Results 



The results of the investigation are summarized in Tables I and II 

 and in Figs. 3 to 9. 



Figs. 3 to 7 — Creosoted southern pine poles: Depth of penetration and per cent 

 of sapwood penetrated in relation to decay in twelve-pound full cell poles in line. 

 Key: Hollow dot indicates decaying pole; solid dot indicates pole failed because 



of decay; cross indicates heartwood decay or slight external decay below 



ground line. 



Fig- ^ — 2393 poles in miscellaneous lines less than ten years (average 7.7 years) 



