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BELL SYSTEM TECHNICAL JOURNAL 



specifications define poles of a quality that the major utilities have 

 found to be satisfactory. Departures from straightness are held within 

 practical limits for ordinary use. 



Decay and the presence of wood-rotting fungi are generally pro- 

 hibited. Minor exceptions are made with respect to the butts of the 

 cedars, which are usually treated with creosote. The question of 

 including poles cut from sound dead trees received careful considera- 

 tion. Blighted chestnut is acceptable with certain restrictions, but 

 in the case of the other three species poles from live timber are speci- 

 fied. While it might appear economical to salvage and use all sound 

 dead trees standing in the woods, practical opinion at present strongly 

 favors eliminating dead timber as a source of pole material because 

 of the extra costs involved in handling and inspection. 



It has proved impracticable to limit checks in a precise manner. 

 Checks or lengthwise separations of the wood fibers vary so much 

 with the age, seasoning, and moisture content of the pole that although 

 definite limitation seemed desirable the compromise finally adopted 

 is one which simply prohibits injurious checks. Practically the matter 

 is left to the judgment of the supplier and consumer concerned. 



100 

 80 



Z[^40 



12 3 4 5 



DIAMETERS, IN INCHES.OF 

 MAXIMUM SINGLE KNOTS 



I 23456789 10 



SUMS OF DIAMETERS, IN INCHES, OF MAXIMUM 



GROUPS OF KNOTS IN 12 INCH SECTIONS 



CURVE A 

 CURVE B 



POLES UP TO AND INCLUDING 45 FEET IN LENGTH 

 POLES 50 FEET AND LONGER 



note: "PER CENT OF POLES" REFERS TO THE PER CENT OF POLES HAVING SINGLE 



KNOTS OR GROUPS OF KNOTS SMALLER THAN THE SIZES INDICATED ON THE BASE 

 LINE. FOR EXAMPLE, 58 PER CENT OF THE POLES 50 FEET AND LONGER HAVE 

 MAXIMUM SINGLE KNOTS SMALLER THAN 3 INCHES IN DIAMETER 



Fig. 2 — Knot sizes in southern pine poles. 



The limitation of knots was a matter of special study. Previous 

 specifications were at variance and data were lacking to establish 

 acceptable limits. Measurements of knots larger than one half inch 

 were therefore made on representative poles of the four species. The 

 size and location of about twenty-three thousand knots in some 567 



