130 THE BELL SYSTEM TECHNICAL JOURNAL, JANUARY 1953 



In Bell Telephone Laboratories, R. E. Waterman and his colleagues 

 started work on a wood-over-water block method for testing wood pre- 

 servatives soon after the St. Louis conference, and they published their 

 early results in 1937 and 1938.'^' ''^' ''^ Their block was a %-inch cube 

 with a hole drilled through it in the approximate center of a transverse 

 face. The J^-inch cubes simply represented sections of the J^-inch square 

 stakes that had been substituted for round saplings^^ in the small speci- 

 men test plot experiments. The hole served a double purpose — it facili- 

 tated handling the blocks during drying and sorting operations'^ ^ and it 

 served as a point of entrance of moisture, which was purposely provided 

 for the block by means of a wood wick. 



Leutritz^^ formalized a soil-block test completely independently of 

 Flerov and Popov, and published his method in this Journal (Vol. 25) 

 in 1946, following an earUer short article in 1939^^ suggesting soil as a 

 culture medium. 



Beginning in the summer of 1944 and continuing until June 30, 1951, 

 Bell Telephone Laboratories subsidized in part a series of studies by the 

 Madison Branch of the Division of Forest Pathology, of the United 

 States Department of Agriculture, Bureau of Plant Industry, in coopera- 

 tion with the Forest Products Laboratory at Madison, Wisconsin. The 

 results of these studies and of parallel investigations have appeared in 

 eight papers"' '''''•''•''• ''''"•'' from 1947 to date. The differences 

 between the agar-block and the soil-block techniques, and the results 

 obtained in comparable test series by the two methods are of funda- 

 mental importance. They are presented and discussed at length in a 

 paper by Duncan."*' Already some 40,000 blocks have been tested by the 

 soil-block method at Madison, with 75 oil-type preservatives. Both at 

 Madison and at Bell Telephone Laboratories, Murray Hill, additional 

 work aimed at further refining of the soil-block technique is under way. 



Subsequent to discussions of the new soil-block techniques between 

 representatives of Bell Telephone Laboratories and of the Forest Prod- 

 ucts Laboratories of Canada, Sedziak'"^ has developed a soil-block test 

 involving burying the block in the soil all but one corner; and instead of 

 placing it on a fungus culture growing on feeder blocks, he inoculates a 

 corner of the test block directly. 



For a general review of laboratory and test plot methods for evaluating 

 wood preservatives the interested reader should have available, in addi- 

 tion to Cartwright and Findlay's book,^* at least two more recent books, 

 namely "Wood Preservation During the Last 50 Years" by van Groenou, 

 Rischen and van den Berge,"* and the third edition of Holzkonservierung 

 by Mahlke-Troschel-Liese/* Hunt and Garratt*^ survey wood preservation 



