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THE BELL SYSTEM TECHNICAL JOURNAL, MARCH 1953 



weathered on the wheel in the same way they did outdoors. Rhodes 

 reaffirms his conclusions about the weathering wheel tests in 1936 in a 

 discussion of the Snell and Shipley paper^^^ in these words: 



"Our consideration of this problem convinced us, and Snell and Ship- 

 ley agree mth the opinion, that natural weathering produced by heat 

 and cold, rain and wind, involves not only evaporation but water leach- 

 ing and mechanical losses of whole oil by water or by bleeding. ... To 

 simulate these conditions, we exposed blocks of wood treated with the 

 test creosotes to variations in temperature, to moving water and to 

 moving air. ... In fact, we believe that our wood-block exposure tests 

 include most, if not all, of the factors of natural weathering. ..." 



Now to go back a bit to Curtin's 1926^^ experiments, this time refer- 

 ring to his own weathering tests on creosoted wood. Table XXVIII is an 

 interpretation of the results he obtained by exposing small blocks, cut 

 from pressure treated 2x4 inch southern pine sap wood stakes, to natural 

 out-of-door weathering. His procedure was extremely severe, but he was 

 aiming at an extreme accelerated test for permanency. After treatment 

 his 2 X 4 inch sample pieces were held in storage under cover for 2 months; 

 and then they were cut up so that the test blocks were about 2x}/^x% 

 inches. These small pieces were exposed 15 feet above the ground on 

 wooden trays for a four-month period from September, 1926, to January, 

 1927, and for a ten-month period from September, 1926, to July, 1927. 

 Losses from the 2x4 pieces that must have occurred during their two- 

 month storage period would increase the loss figures shown in the table. 

 The losses are obviously greater for the lighter treatments, and for the 

 lower residue oil. 



Table XXVIII — Creosote Losses prom Southern 

 Pine Blocks* 

 Outdoor weathering tests — Based on data by Curtin.32 



* See text for description of blocks 



t Creosote number 1 was a domestic oil, specific gravity 1.056 and residue above 

 355°C of about 26 per cent; number 2 was a British oil, specific gravity, 1.068 

 and residue above 355°C of about 19 per cent. 



