132 THE BELL SYSTEM TECHNICAL JOURNAL, JANUARY 1953 



leading to the development of preservative evaluation methods to sup- 

 plement or partly displace long and uncertain service tests. The authors 

 present a mass of information on six different creosotes, on four creosote 

 fractions, and on mixtures of the creosote with fuel oil of Persian origin. 

 Sal (Shorea robusta) railway ties were used for the field trials. Many of 

 the data are condensed into graphs that are small and difficult to read. 

 The findings in general are favorable to the creosote-petroleum blends. 

 The writer, on the basis of personal experience, is dubious about either 

 the theoretical or practical significance, in experiments of the type re- 

 ported, of the values given for standard deviations and standard errors. 

 The scope of the work entitles it to more complete review than is prac- 

 ticable at this particular time and place. 



Bell Telephone Laboratories are represented in a group carrying 

 on comprehensive cooperative investigations of pedigreed creosotes on 

 which four papers have already been published.^' ^^' ^^' ^^ 



The results of outdoor tests of small stakes and fence posts are issued 

 periodically by the Forest Products Laboratory at Madison, Wis.^^* ^^' 

 ^^' ^^ In this connection, the Proceedings of the American Wood-Pre- 

 servers' Association are in the class of required reading. Additional ref- 

 erences will be cited at appropriate points in the succeeding paragraphs. 



Data will first be presented on some of the experience of Bell Tele- 

 phone Laboratories and others with laboratory soil-block tests, with 

 outdoor tests of small stakes, of pole-diameter posts, and with pole test 

 lines in evaluating wood preservatives. Through analysis and discussion 

 an attempt will be made to interpret the significance of the results ob- 

 tained by the various evaluation procedures and to correlate the evi- 

 dence. Emphasis will be placed naturally on creosote and pentachloro- 

 phenol because of their great importance to the Bell System pole plant. 

 The writer intends to support his interpretations with experimental data 

 wherever possible, reserving the privilege in some cases to make sugges- 

 tions ais to possible significance, even though complete technical proof 

 may be lacking at present. 



EVALUATION BY SOIL-BLOCK TESTS 



General Procedures 



Soil-block cultures have been described in a number of papers^^' ^^' ^^' 

 ^' ^* since Leutritz presented his method in this Journal in 1946.^° 

 Some of the following statements, therefore, will be repetition; but the 

 intent is to outhne the technique employed at Bell Telephone Labora- 

 tories as a base for later discussion. 



