FOREST SERVICE. 407 



Drying of Wood. 



In continuation of past studies of air seasoning, experiments were 

 made witli eucalyptus. The data obtained show the rate of season- 

 ing and the extent of checking in trees cut in different locaUties and 

 at .different times of tlie year. The primary object sought is to learn 

 how to get the best results when eucalyptus is to be cut for poles 

 and piling. 



Because of the time required to air-season wood artificial methods 

 of drying are almost universal, especiall}^ for liigh-grade lumber. All 

 such methods have proved more or less imperfect, and it is conserva- 

 tively estimated that 10 per cent of the material dried in kilns is 

 ruined or greatly lowered in value b^ excessive checking and warp- 

 ing. To stud}^ the fundamental principles of drying in kuns operated 

 at atmospheric pressure an expermiental k^ln was erected, so designed 

 as to secure control of the temperature, air circulation, and humidity, 

 the three elements upon wliich the drying of lumber depends. A 

 small commercial kiln embodying the same principles of construc- 

 tion, erected by a private company at Oakland, Cat, will make pos- 

 sible experiments to determine the best methods of kiln-drying dif- 

 ferent species of eucalyptus. 



Arrangements were also made for a series of experiments to per- 

 fect methods of kiln-dr3dng hickory stock used by the vehicle and 

 implement industries. At present it is necessary to air-season most 

 of the liickory stock used by these industries, with considerable loss 

 from the attacks of wood borers and with added expense for handling. 



Strength Tests. 



The timber-test investigations of the year may be divided into 

 three general classes: 



(1) Standard tests upon the commercial timbers of the United 

 States to determine their relative strength, stiffness, toughness, 

 hardness, cleavabihty, and other mechanical properties. The knowl- 

 edge thus gained enables manufacturers and other users to employ 

 the different woods most advantageously, and often to substitute 

 less well-lvnown woods for woods which are becoming scarce. The 

 tests in this class are made on clear specimens of comparatively 

 small size. 



(2) Tests on structural forms and sizes of timber, to furnish 

 engineers and architects with data on the strength and other mechan- 

 ical properties of woods used in construction, particularly as regards 

 species and classes of wood which are not fully utilized. 



(3) Tests to determine the influence of preseiwative treatments, 

 methods of seasoning, and other processes on the mechanical prop- 

 erties of wood. 



A plan for the comprehensive study of the commercial timbers of 

 the United States provides for the securing of data which not only 

 will show the relative mechanical properties of the different species 

 studied but also will be of great value in determining under wiiat con- 

 ditions of growtli the b(>st wood is produced in a given species. 

 Tests were made upon white oak, red oak, and white ash from Louisi- 

 ana; black spruce, white spruce, red spruce, and balsam fir from 

 New Hampshire; and red oak, white ash, rock elm, and hard maplo 



