294 STRENGTH OF MATERIALS 



(1) That large, sound beams may be as strong as small ones < -ut 

 from the same piece; that is, large beams may show the same liber 

 stress as small ones. 



(c) That large, sound pieces in compression may be as stmi 

 small ones cut from the same piece; that is, the intensity of >ni- 

 pressive stress may be the same. 



(d) That there were no detrimental effe< 



The results of the tests made by the Bureau of Forestry, a- ..in- 

 lined in this article, should not be taken as conclusive, sin< not a 

 sufficient number of tests were made to establish values. Tin- pieces 

 were in most cases small, and specially selected, and the results are 

 of more value from a scientific than from a commercial standpoint, 

 since the lumber of commerce contains knots, wind shakes, and other 

 defects that lessen its strength. 



246. Recent work of the Bureau of Forestry. At the j.r 

 time (1906) the Bureau of Forestry, under the direi -ti.in f ! 

 \V. K. Matt nt' Purdue I'niversity, is carrying out tests designed t<> 

 valuable information to engineers, architects, lumbermen, and 

 others on the strength of commercial lumber. The following is an 

 outline of the tests now under way.* 



1. Tests of tin- ineehaiiical and phv-iral pn.jM-rties of tiinl..-i- in f..rni> found 

 on tin- market. Tin- material will U- <f the same >!/ ami tirade as commercial 

 products. The purpose is to determine moduli determine the 



value of woods now < .iiMd.T.'d inferior; to determine tin- liability to knots 

 and the reducing factors due to these; to arrange a table of standard \\eighte, 

 and rules of in>]K-ction and grading; and partly to compare th.- j.rojH-rties of 

 species from different region-. 



J. The effect of rate of apj.li.-ation of load, including impact tests. 



3. The effect of moist urr. 



4. The effect of preservati 



5. The effect of met h Boning. 



6. The effect of fire retardants. 



The test pieces for 1 are large commercial pieces in which k 

 and other defects occur, as they do in the structural timbers used by 

 engineers. 



A summary of some of the cross-bending tests of 1, already made, 

 is given in the following table. 



* " Progress Report on the Strength of Structural Timber," Bureau of Forestry Circular. 



