20 



AMERICAN WORK. 



While it may be possible to work out the general laws of relation lietweeu physieal aud 

 mechauical properties on material of European origin, for practical jiurposes we can uot rely upon 

 any other data thau those ascertained from American timbers, and so far as dependence of qiuil- 

 ity on conditions of growth are concerned this truth is just as jiatent. Although in the United 

 States probably more timber has been and is being used than in any other country, but little work 

 has been done in the domain of timber jjhysics. 



Among the earliest American experiments falling in the domain of timber physics, may be 

 cited those of Marcus Bull, to determine "the comparative (luantities of heat evolved in the 

 combustion of the principal varieties of wood and coal used in the United States for fuel," nuide in 

 the years 182;5 to 1.S25 and published in 1826. Here the experiments of La\oisier, Crawford and 

 Daltou, aud Count Rumford on similar lines are discussed and followed by an able series of exper- 

 iments and discussion on American woods and coals. 



The only comprehensive work in timber physics ever undertaken on ^Vmericau timl)ers is that 

 of Mr. T. P. Shabples, in connection with the Tenth Census, and published in 1SM4, vol. ix 

 on the Forests of North America. Comprehensiveness, however, has been sought rather in 

 trying to bring under examination all the aborescent species thau in furnishing fuller data of i)rac- 

 tical applicability on those from which the bulk of our useful material is derived. "The results 

 obtained," the author says, "are highly suggestive; they must not, however, be considered con- 

 clusive, but rather valuable as indicating what lines of research should be followed in a more 

 thorough study of this subject." 



Not less than 412 species were examined in over 1,200 specimens. The results are given in 

 live tables, besides four comparative tables of range, relative values, averages, etc. The specimens 

 were taken "in most cases from the butt-cut and tree from sap and knots;" the locality and soil 

 from which the tree came are given in most cases, and in some its diameter aud layers of heart and 

 sapwood; determinations were made of specific gravity, mineral ash per cent, and fi-om these data 

 fuel values were calculated. 



The specimens tested were "carefully seasoned." P\>r transverse strain they were made 4 

 centimeters (1.57 inches) scpiare, and a few of double these dimensions, with 1 meter (3.28 feet) span. 



One table illustrates "the relation between the specitic gravity and the transverse strength of 

 the wood of species, upon which a suflicieut number of tests has been made to render such a com- 

 parison valuable." This table seems to show that in perfect specimens weight and strength 

 stand in close relation. A few tanning determinations on the bark of a few species are also given. 



The object of the work as stated, namely, to be suggestive of a more thorough study of the 

 subject, has certainly been fully and creditably attained. Of compilatory works, for use in prac- 

 tice aud for refercnice, the following, published in the United States, may be cited : 



De VoLSON Wood: Kesistauce of Materials (1871), containing rather scanty references to 

 the work of Chevandier aud Wertheim. 



li. G. Hatfield: Theory of Transverse Strain (1877),which, besides other references, contains 

 also twenty-three tables of the author's own tests on white i)ine, Georgia i)ine, hemlock, spruce, 

 white ash, and black locust, on sticks 1 by 1 inch by l.C feet in length. 



William H. Bure: The Elasticity and Kesistanceof Materials of Engineering, third edition, 

 1890, a comprehensive work, in which many references are made to the work of various American 

 experiuienters. 



Gaetano Lanza, in Applied Mechanics, 1885, lays especial stress on the fact that tests on 

 small select pieces give too high values, and quotes the following experiments on long pieces. He 

 refers to the work of Capt. T. J. IiODMAX, U. S. Army, published in Ordnance Manual, who used 

 test pieces 25 by 5i| inches and 5 feet length without giviug any reference to density or other facts 

 concerning the wood ; and to Col. Laidley's U. S. Navy tests (Ex. Doc. 12, Forty-seventh Cougi-ess, 

 first session, 1881), who conducted a series of exi)eriments on Pacific shipe timbers, "white and 

 yellow pine," 12 feet long and 4 to 5 by 11 to 12 inches scpiare, giving also account ol' density and 

 average width of rings. 



