490 THE BELL SYSTEM TECHNICAL JOURNAL, MARCH 1953 



the lead. However, there have been a total of three failures in the creo- 

 soted stakes treated with average retentions of 3.6 (two stakes) and 5.6 

 (one stake) pounds of creosote. Stakes treated to an 8.6 pound retention 

 are showing slight to medium decay, and in two plots slight decay has 

 been found on a total of three stakes treated to a 12.1 -pound retention. 

 The stakes are all treated without the addition of any diluent, such as 

 toluene, to the creosote. The reader, bearing in mind the differences in 

 the site conditions, can make interesting comparisons between the small 

 stake test results obtained in Sweden and in the Gulf port test plot. 



Of further interest, however, is the fact that in the Swedish tests, 

 round posts treated with average retentions of 5.37 and 5.80 pounds 

 per cubic foot are all rated as sound after seven years exposure. One 

 can assume that at treatment the outer annual rings of such posts con- 

 tained 8 pounds or more of creosote and this amount has been sufficient 

 to protect the posts in the Swedish climate. Rennerfelt has stated per- 

 sonally to the writer that one would have to proceed with caution in 

 Sweden in the direction of increasing the creosote retention for poles, on 

 account of public reaction against bleeding. His test results — the only 

 ones of their kind available from Europe to the writer's knowledge — 

 seem to be in line with Bell Telephone Laboratories findings. They would 

 be more interesting if he had used soil-block tests for correlation. 



Shortening the Bioassay Test 



Besides speeding up the weathering period by the use of a weathering 

 wheel, or by the method of alternating water and controlled heat cycles 

 now being developed at Bell Telephone Laboratories, there are two other 

 avenues of approach to shortening the bioassay test. One is the use of 

 thin wood veneer test units in place of wood blocks, in the methods of 

 impregnation and exposure to fungus action proposed by Breazzano ' 

 and Hopkins and Coldwell.^^ Breazzano claims a maximum of accuracy 

 because of uniform distribution in thin pieces of wood, 0.6-0.7 mm, of 

 the preservative to be tested and because the fungus attack and passage 

 through the thin strip gives a quick visual indication of the necessary 

 protective threshold. He also claims advantages for his Italian method 

 because it is not necessary to use any culture medium at all — he ex- 

 posed his wood strips over water only (cf . Waterman et al^^^) — and 

 because no tedious weighing techniques and record making are required. 

 His arguments are intriguing, but his method seems to be quite out of 

 question for testing toxicity-permanence relations of volatile preserva- 

 tives like creosote. Evaporation losses would be very rapid, close to those 



