ADMINISTRATION 109 



other chemical products of wood. This work is 

 carried on at the Laboratory and sometimes in 

 cooperation with the National Forests and district 

 experts. At the Laboratory there is a director 

 and a large staff of technical and scientific men, 

 such as chemists, physicists, and engineers, each of 

 whom is an expert in his particular line of work. 



A good deal of attention is given to testing the 

 strength of woods grown in the United States, as 

 a means of assisting users to select the species best 

 adapted to a given purpose, or to find substitutes 

 for species which are becoming difficult to obtain. 

 The strength of a good many species used for 

 structural timbers has been tested. The species 

 most used for this class of timber are the Southern 

 j)ines, Douglas fir, Norway pine. Tamarack, and 

 Red spruce. An important discovery was made 

 several years ago that Western hemlock, generally 

 considered an inferior timber, showed an average 

 strength 88 per cent, as great as that of Douglas 

 fir, one of the best construction timbers in the 

 United States. Strength tests have also been 

 made on fire-killed timber and these have shown 

 that timber killed by fire is almost as strong as 

 green timber. Other tests have been made to de- 



