FOREST SEEVICE. 247 



and abroad as of immense value to science and industry. In all, the 

 investigations of the Laboratory have cost about $2,000,000 and are 

 believed to be now saving industry at least $30,000,000 annually. But 

 its value is not confined to such benefits. If the material from an 

 acre of forest can be made to go twice as far or to last twice as long 

 as formerly the result is the same as if the production of that acre 

 were doubled. Investigations leading to the more efficient utilization 

 of forest products are thus an integral part of any comprehensive 

 program aimed at the perpetuation of our forest resources. 



The ending of the war did not terminate investigations connected 

 with the national defense. Many projects undertaken during the 

 war were comj^leted and a number of new projects were started, 

 including the design of various types of airplane struts and the de- 

 velopment of a plywood airplane wing. Extensive tests were made 

 on white ash and other species to determine the effect of spiral grain 

 and of various other defects and blemishes on strength. 



In addition to specific designs the closer utilization of existing 

 supplies of aircraft woods was investigated and types of built-up 

 beams Avere developed. The laboratory will make investigations 

 connected in one wa}' or another with the national defense a part of 

 its regular program, in cooperation with the War and Navy Depart- 

 ments. 



Knowledge of the mechanical properties of wood was extended 

 through 62,000 tests, covering 57 different species. The total number 

 of such tests made by the laboratory is now 500,000. Among the 

 subjects of investigation were the effect of commercial processes of 

 wood ]:>reservation on the strength of structural timber, the tough- 

 ness and shearing strength of various kinds of plywood, its bolt- 

 bearing and screw-fastening proi)erties, and the impairment of 

 strength of Avood under continuous vibration. The services of the 

 box-testing laboratory were extensively used by manufacturers and 

 shippers. Several private box-testing laboratories modeled on that 

 at Madison have been built. The best methods of packing various 

 commodities, such as shoes, phonographs, cream separators, and 

 scrul)l)ing machines, and the design of containers of the highest effici- 

 ency and lowest cost, were subjects of continuous study. Tests of the 

 value of western woods for box making resulted in establishing 

 white fir, formerly thought to be of little value for boxes, as a com- 

 mei'ciid box wood. 



Further studies were made to improve the formulas for water- 

 proof glues for plywood manufacture. Information on the prepara- 

 tion and use of various glues was furnished to numerous commercial 

 manufacturers. Special courses of instruction were given to repre- 

 .sentativos of glue and plywood users. 



The study of stresses in composite pieces of wood glued in varying 

 combinations was completed, with results that will be of value in all 

 kinds of built-up construction. Studies of the conditioning and 

 manufacture of airplane propellers were continued and recommenda- 

 tions made for the revision of present manufacturing specifications. 

 Manufacture and test of various types of joints and s])lices in pro- 

 peller laminations furnished information of value to propeller manu- 

 facturers and others whose work requires the joining of pieces to 

 form large boards. 



