TIMBER 291 



244. Tests made for the tenth census. In the United States, tests 

 were made for the tenth census on four hundred and twelve species 

 of timber. The test specimens were all small, selected pieces, 1.57 in. 

 X 1.57 in. in cross section, and 43 in. long, and were seasoned in a 



dry, cool building for two years. On account of the number of 

 species tested the results obtained are not conclusive, but should 

 be taken as indicating the probable values for the strength of the 

 timbers tested. On page 290 is given a table of the averages for some 

 of the species tested. Since the test pieces were all small, selected 

 specimens, the results are probably higher than would have been 

 obtained from larger commercial specimens. 



In the transverse tests the specimens were supported at both ends 

 and loaded in the middle, the span being 39.37 in. The compression 

 tests parallel to the grain were made on pieces 1.57 in. x 1.57 in. in 

 cross section, and 12.6 in. long. Indentation tests were made on 

 pieces 1.57 in. x 1.57 in. in cross section and 6.3 in. long. The test 

 pieces in the latter case rested upon the platform of the testing 

 machine, and the tests were made by crushing perpendicular to the 

 grain with a plate 1.57 in. X 1.57 in. in size, by lowering the moving 

 head of the machine. 



245. Tests made by the Bureau of Forestry. The most extensive 

 series of timber tests that has ever been undertaken has been begun 

 l>y thf I'nited States Department of Agriculture under the direction 

 of the Bureau of Forestry. These tests were begun in 1891, under 

 the direction of Professor J. B. Johnson, at St. Louis. Thirty-two 

 species were tested and 45,000 tests were made. The material was 

 selected with special reference to the conditions under which the 

 trees were grown, and the test pieces were small, selected speci- 

 mens. The table on page 292 gives the average results of some of 

 the tests.* 



In the table the results have been reduced to an amount of moist- 

 ure equivalent to 12 per cent of the dry weight. 



A comparison of this table with that of the tenth census shows as 

 close an agreement in most cases as might be reasonably expected 

 when the variability of timber is considered, and serves to extend 

 and verify the results of the previous work. 



* U. S. Forestry Circular, No. 15. 



