408 ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE. 



from Wisconsin. Specimens of other species for future tests were 

 secured from the Ohio River Valley and the Rocky Mountain region. 



Tests to determine the strength of bridge stringers and car sills, 

 and to determine the effect of knots and checking on the strength 

 of such timbers, were completed during the year. Tests were also 

 made of Douglas fir stringers and joists cut from fire-killed timber, 

 of which enormous quantities are going to waste in the West. The 

 tests show conclusively that fire-killed fir, if manufactured into lumber 

 before it is attacked by insects and decay, is practically as good for 

 structural purposes as material secured from the living tree. 



Much of the timber growing at liigh altitudes in the Rocky Mountain 

 region is too small for the manufacture of lumber and other saw- 

 mill products, but is used in mining and miscellaneous construction 

 work. The supply of Douglas fir, until recent years almost entirely 

 depended upon ^iroughout Colorado and Wyoming for mine timbers, 

 is now growing scarce in the vicinity of most of the mining camps^ 

 and other species must be used. To aid in meeting this situation, 

 tests were made to find out whether fire-killed timber could be 

 advantageously used, and to determine how lodgepole pine, Engel- 

 mann . spruce, bristle-cone pine, western yellow pine, and Alpine 

 fir compare in strength with Douglas fir. The results -will shortly 

 be available. Tests made primarily to ascertain the value of lodge- 

 pole pine and Engelmann spruce, as compared with red cedar, for 

 telephone and telegraph poles showed that lodgepole pine was 

 approximately 80 per cent as strong as red cedar and that Engelmann 

 spruce may therefore frequently be used to advantage in lighter 

 construction work. 



The increasing use of bridge timbers treated with coal-tar creosote 

 has made the question of the influence of such treatments on the 

 strength of the stringers one of considerable importance to bridge 

 engineers. A series of tests to determine the effect of preservative 

 treatments with creosote on the strength of yellow pine and Douglas 

 fir stringers, started in 1908, is now nearing completion. 



Much damage is caused annually by the stainmg of yellow-pine 

 lumber. Various chemicals, principally bicarbonate of soda, are 

 used to prevent such stain. There were many objections to the 

 use of material treated in this manner, because it was claimed that 

 the treatment affected the mechanical properties of the wood. A 

 series of tests made in cooperation with the Yellow Pine Manufac- 

 turers' Association to ascertain whether or not this contention was 

 justified showed that the treatment has no appreciable effect uDon 

 the properties of yellow-pine wood. 



Wood Preservation. 



In 1910 the amount of wood treated in the United States exceeded 

 100,000,000 cubic feet; tins was over 500 per cent more than that 

 treated in 1904. The rapid extension of wood preservation into new 

 fields and the treatment of new woods have developed many practical 

 problems concerning which little or nothing is known; in fact, the 

 whole industry is of such recent development that the knowledge 

 of the fundamental principles upon which it is based is very meager. 

 The wood-preservation investigations of the Forest Service may be 

 divided into the following classes: 



