644 ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE. 



high boiling fractions, which appear to plug up the outer cells and 

 so insure the retention of the lighter oils in the interior of the wood. 

 In the paving-block tests preliminary results throw an interesting 

 light on the relative efficiency of " heavy " and " light " oils in treat- 

 ing this class of material. 



A ])erplexing problem in connection with the preservative treat- 

 ment of ties is how to obtain a uniform treatment of all ties in any 

 one cylinder charge. To accomplish this it is essential that only 

 timbers which present the same degree of resistance to penetration be 

 treated together. Tests to establish a scale of penetrability have been 

 completed on a large number of coniferous woods and the results are 

 now being analj'zed. The w^ork will be continued on woods of the 

 broadleaf trees. 



To determine the relative resistance of various untreated woods to 

 decay, specimens were subjected to pure cultures of fungi in jars. 

 The tests have not been under way long enough to give definite results. 



To find a preservative treatment for poles used in the construction 

 of telephone lines upon national forests which can be applied locally 

 and at small cost, preliminary tests with the Boucherie process, which 

 has been successfully used in Europe, were made on several national 

 forests in California. This process consists, briefly, of impregnating 

 freshly cut poles with a solution of copper sulpliate, aided by the 

 osmotic action of the wood cells. Experiments already made have 

 been very encouraging, and more extensive ones have been undertaken. 

 If the process is found to be feasible for this country it should find 

 extensive use by commercial companies, especially in the more remote 

 regions. 



A series of tests to determine an economical method for treating 

 paving blocks of Douglas fir and w^estern hemlock, undertaken in co- 

 operation with the University of Washington, showed that a cheap 

 and efficient treatment can be obtained by the open-tank process. 

 Preliminary tests on western larch blocks indicate that this species 

 is adapted to the same method of treatment. 



Experimental treatment of a large nmnber of red oak and hard 

 maple cross-ties, to determine the relative efficiency of diflerent proc- 

 esses, was completed at the close of last year. The treated ties, to- 

 gether with a number of untreated ones — about 1,700 in all — have been 

 laid in a test track of the Chicago, Milwaukee & St. Paul Railway Co., 

 m cooperation with which the work was undertaken. Inspections 

 of the test track will be made at least once each year to determine the 

 condition of the ties in respect to decay and rail wear. 



Exact knowledge concerning the preliminary vacuum or pressure, 

 the rate at which heat is transmitted to the interior of the wood from 

 the surrounding medium, and the manner in which a liquid permeates 

 wood must be had before any real advance in methods of impregnat- 

 ing woods can be expected. Studies were therefore made during the 

 year of the rate at which air pressure or vacuum is transmitted 

 through wood and the effect of preliminary vacuum or pressure upon 

 absorption and penetration of the preservative, the recovery of the 

 preservative after injection, and the loss after treatment by dripping 

 and volatilization. Other studies dealt with the relation of certain 

 structural features, such as tyloses, resin canals, and bordered pits, to 

 permeability of the wood. 



