EVALUATION OF WOOD PRESERVATIVES 123 



inate other species on the West Coast and in the Pacific Northwest, 

 while pressure and non-pressure treated lodgepole pine poles are favored 

 in the Mountain States area. Pressure-treated jack pine and ponderosa 

 pine move into telephone plant in small quantities in the Lake States 

 and in the California areas, respectively. 



To render telephone service the Bell System has some 20,000,000 wood 

 poles carrying its wires and cables. Many of these poles are used jointly 

 with the power companies. Since poles of the joint use sizes are not 

 available in sufficient quantities in the southern pine forest to meet all 

 the demands of the utilities all of the time it is inevitable that western 

 cedar, Douglas fir, lodgepole pine, red pine and western larch should 

 move into various parts of the System, either for the direct and sole use 

 of the Operating Companies or for joint use. 



The pole plant is continually changing. Pole species from the North- 

 west vary greatly in their treatability and they are generally harder to 

 treat than southern pine. It is not possible to use traditional creosote 

 pressure treatments for some of these species without running the risk of 

 objectionable exudation, or bleeding, of the creosote. 



The development of practical specifications for the application of new 

 preservatives such as pentachlorophenol and greensalt, as well as the 

 various types of creosote, to all of the pole species now used in Bell 

 System plant calls for setting as exactly as possible necessary protective 

 quantities of the various preservative materials. This is particularly true 

 in view of the fact that for normal telephone use as well as for joint use 

 it is absolutely essential to deHver to the Operating Companies poles 

 that are clean and satisfactory for use in all types of telephone lines, 

 without compromising on the question of adequate physical life for the 

 treated units. This purpose is back of the Laboratories' efforts to develop 

 bioassay tests that come as close as practicable to measuring the neces- 

 sary protective amount of any given preservative, and to predicting its 

 relative permanence in poles and crossarms in plant. 



It has been pointed out in earlier papers^"' ^^' ^^ that Bell Laboratories' 

 concept of preservative evaluation involves (a) laboratory evaluation 

 tests, (b) test plot experiments with small stakes, (c) similar tests of 

 pole size specimens, and (d) test fines selected for long time observation. 

 The latter are chosen with the cooperation of the Operating Companies. 

 Lumsden^^ has recently presented a summary of a quarter century of 

 experience with pole-diameter posts in one test plot located at Gulf port, 

 Mississippi. The principal aims of the present paper are to interpret the 

 results of various laboratory methods of preservative evaluation, and to 



