406 ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE. 



June, 1010. Furnislied with the most complete modern equipment 

 and with a well-organized staff of experts, the Service is now able 

 to conduct its roscarcli work in forest products with an effectiveness 

 impossible under the oltl conditions. 



The work as now organized comprises studies in the physical ])rop- 

 erties of wood, the drying of wood, strength tests, wood preservation, 

 wood distillation, wood pulp and paper, naval stores, and wood 

 utilization. 



The Physical Properties of Wood. 



The laboratory aims not only to obtain facts regarding the qualities 

 of wood and their behavior under different conditions, but in all 

 cases to find the underlying causes. Structural characteristics ex- 

 plain the peculiar mechanical properties of a given wood. Explana- 

 tion of the fact that different species require very different preservative 

 treatment is found in differences in their physical qualities, as shown 

 by the microscope. A study of the structural qualities of the various 

 woods, therefore, is carried on side by side wath the strength tests, 

 the preservative tests, and the other investigations. 



As a means of carrying out these studies there were prepared during 

 the year about 1,000 microscopic slides, representing 74 different 

 species. 



To determine the ability of wood to withstand the strain of con- 

 tinuous loads to which its use in structural work subjects it, a series 

 of dead-load tests was made, supplementing similar tests previously 

 made on long-leaf pine. A series of determinations of the specific 

 gravity of the solid matter in different w^oods is under way. The 

 density of wood, which determines many of its physical and mechan- 

 ical properties, depends upon the relative amounts of solid matter 

 and open spaces; knowing the specific gravity of the former, the 

 amount of the open spaces may be calculated. 



Very little is kno\Mi concerning the behavior of wood when sub- 

 jected to high pressures and high temperatures or to various other 

 conditions of the surrouncdng medium. Preliminary tests indicate 

 that the strength, density, and hardness as well as the hygroscopicity 

 of wood may be greatly affected by such conditions. They also 

 indicate that by a proper manipulation of the treatment it is possible 

 to entirely penetrate mth preservative fluids s])ruce, hickory, and 

 other woods which in their natural state are relatively impervious to 

 injection. 



The hygroscopicity of woods is of prime importance, both in con- 

 nection with kiln-drying and in aU ca-ses where shrinking and swelhng, 

 or "worldng, " of the wood after manufacture enters into the prob- 

 lem of its use. This subject was studied in prelimhiary tests. The 

 specific heat of wood was studied in a series of careful experiments. 

 This is the first time that this subject has been investigated in a 

 comprehensive manner. The results show that the specific heat of 

 all woods is approximatelv the same irrespective of species, the mean 

 value between 0° C. and" 106° C. being 0.327. These results are of 

 considerable scientific importance and will prove of value in the 

 experiments being conducted on the kUn-drying and preservative 

 treatment of timber products. 



