382 FORESTRY INVESTIGATIONS U. S. DEPARTMENT OF AGRICULTURE. 



The specimens tested were "carefully seasoned." For transverse strain they were made I centimeters (1..77 

 inches) square, and a few of double Hiese dimensions, with t meter (3.28 feet) span. 



One table, illustrates "the relation between the specific gravity and the transverse strength of the wood of 

 species, upon which a sufficient number of tests has been made to render such a comparison valuable." This table 

 seems to show that iu 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 practice and for reference, the 

 following, published in the United States, may be cited: 



De Volson Wood: Resistance of Materials (1871), containing rather scanty references to the work of Chevandier 

 and Wertheiui. 



It. (i. Hatfield: Theory of Transverse Strain (1877), which, besides other references, contains also twenty-three 

 tables of the author's own test on white pine, Georgia pine, hemlock, spruce, white ash. and black locust, on sticks 

 1 by 1 inch by 1.6 feet in length. 



William H. Burr: The Elasticity and Resistance of Materials of Engineering, third edition, 18110, a compre- 

 hensive work, in which many references are made to the work of various American experimenters. 



Gaetano Lanza, iu 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. .1. 

 Rodman, United States Army, published in Ordnance Manual, who used test pieces '21 by 5; inches and 5 feet length, 

 without giving any reference to density or other facts concerning the wood ; and to Col. Laidley's United States 

 Navy test (Senate Ex. Doc. 12, Forty-seventh Congress, first session, 1881), who conducted a series of experiments on 

 I'acilic slope timbers, " white and yellow pine," 12 feet long and 4 to 5 by 11 to 12 inches square, giving also 

 account of density and average width of rings. 



Lastly, the author's own experiments, made at the Watertowu Arsenal for the Boston Manufacturers' Mutual 

 Fire Insurance Company, on the columnar strength of " yellow pine" and white oak, 12 feet long and 6 to 10 inches 

 thick, are brought in support of the claim that such tests show less than half the unit strength of those on small 

 pieces. Data as to density, moisture, or life history of the specimens are everywhere lacking. 



R. H. Thurston, Materials of Engineering, 1882, contains, perhaps, more than any other American work on the 

 subject, devoting, in Chapters II and III, 117 pages to timber and its strength, and in the chapter on Fuel several 

 pages to wood and charcoal, and the products of distillation. It also gives a description of some twenty-five kinds 

 of American and of a few foreign timber trees, with a description of the structure and their wood in general; 

 directions for felling and seasoning; discusses briefly shrinkage, characteristics of good timber, the intlneneo of 

 soil and climate on trees and their wood, and of the various forms of decay of timber, methods of preservation and 

 adaptation of various woods for various uses, much iu the same manner :m Raukine's Manual of Civil Engineering 

 from which many conclusions are adopted. The author refers, besides foreign authorities, to the following 

 American investigators : 



G. H. Corliss (unpublished?) is quoted as claiming that proper seasoning of hickory wood increases its strength 

 by 15 per cent. 



R. G. Hatfield is credited with some of the best experiments on shearing strength, published in the American 

 House Carpenter. 



Prof. G. Lanza's experiments are largely reproduced, also Trautwine's on shearing, and some of the author's 

 own work on California spruce, Oregon pine, and others, especially in torsion, with a specially constructed machine, 

 an interesting plate of strain diagrams accompanying the discussion. 



In connection with the discussion by the author on the influence of prolonged stress, there is quoted ,'is one 

 of the older investigators, Herman Hanpt, whose results on yellow pine were published in 1871 (Bridge 

 Construction). 



Experiments at the Stevens Institute of Technology are related, with the important conclusion that a load 

 of tiO per cent of the ultimate strength will break a stick if left loaded (one small test piece having been left loaded 

 fifteen months with this result). 



In addition the following list of references to American work in timber physics is here inserted, with a regret 

 that it has not been possible to include all the stray notes which may be in existence but were not accessible. Those 

 able to add further notes are invited to aid in making this reference list complete: 



Abbott, Arthur V. Testing machines, their history, construction, and uso. With illustration!! of machines, includ- 

 ing that at Watertown Arsenal. Van Nostrand's Magazine, 1883, vol. 30, pp. 204, 325, 382, 477. 

 Day, Frank M., University of Pennsylvania. The microscopic examination of timber with regard to its strength. 



Read before American Philosophical Society, 1883. 



Estrada, E. D. Experiments on the strength and other properties of Unban woods. Investigations carried on in 

 the laboratory of the Stevens Institute. Van Nostrand's Magazine, 1883, vol. 29, pp. 417.441. 



Flint, . Report of tests of Nicaraguan woods. Journal of Franklin Institute, October, 1887, pp. 289-315. 



Goodale, Prof. George L., Harvard University. Physiological Botany, 1885, chapters 1, 2, 3, 5, 8, 11, and 12. 

 Ihlseng, Magnns C., Ph. D. On the modulus of elasticity in some American woods, determined by vibration. Van 

 Nostrand's Maga/ine, 1878, 19. 



On a mode of measuring the velocity of sounds in woods. Read before the National Academy of Science, 



1877; published in American Journal of Science and Arts, 1879, vol. 17. 



Johnson, Thomas II. On the strength of columns. Paper read at annual convention of American Society of Civil 

 Engineers, 1885. Transactions of the Society, vol. 15. 



