SCIENCE 



NEW YORK, NOVEMBER 13, 1891. 



GOVERNMENT TIMBER TESTS. 



In reply to many inquiries regarding the compreliensive 

 timber tests inaugurated in the Forestry Division of the De- 

 partment of Agriculture, the following brief statements re- 

 garding the objects and methods of the work have been pre- 

 pared by B. E. Fernow, chief of the division, in the hope 

 that thereby an interest in this investigation, a work of na- 

 tional importance, may be spread. 



It will be admitted by all who have to handle wood in 

 building, engineering, and manufacturing, that our knowl- 

 edge regarding the properties of our various timbers is not 

 very satisfactory, and that while attempts more or less sys- 

 tematic have been made to determine these properties, and 

 knowledge gained from experience exists among those who 

 liave handled certain classes of wood for certain purposes, 

 there does not exist much reliable published information for 

 general use. 



The reason for this deficiency may be explained from the 

 fact that wood, being a non-homogeneous material, varies 

 very largely in its qualities. Not only does there exist a 

 wide range of qualities in the same species if grown under 

 different conditions, but the quality varies in the same tree 

 from the butt to the top, and from the heart to the bark. 



To arrive, then, at any satisfactory results in an experi- 

 mental determination of the properties of wood, it is necessary 

 to derive them from test material of known origin, and, fur- 

 thermore, to establish any laws which will be generally ap- 

 plicable in referring quality to physical appearance, structure, 

 and origin of material, it is necessary to examine and test 

 carefully a very large number of test specimens. 



The difficulty for private enterprise to secure the test mate- 

 rial in sufficient quantity, and with a full knowledge of its 

 origin, in fact the magnitude of an investigation of this kind, 

 renders it pre-eminently an undertaking for a government 

 agency. This has also bsen recognized by the Prussian Gov- 

 ernment; but the United States Department of Agriculture 

 can boast of having inaugurated such elaborate work one 

 year earlier. 



The object of this work in general will be readily perceived 

 from the foregoing statement. 



Besides more reliable data regarding the properties of our 

 principal timbers, there is to be gained from this investiga- 

 tion a means of determining quality by the examination of 

 physical appearance and structure, and of establishing an 

 inter-relation between quality and conditions of growth. 



To deSne the objects of the work more in detail, some of 

 the questions which it is expected ultimately to solve may be 

 formulated as follows: — 



What are the essential working properties of our various 

 woods and by what circumstances are they influenced ? 

 What influence does seasoning of different degree have upon 

 quality ? How do age, rapidity of growth, time of felling, 

 and after-treatment change quality in different timbers ? In 

 what relation does structure stand to quality ? How far is 

 weight a criterion of strength ? What macroscopic or 



microscopic aids can be devised for determining quality from 

 physical examination ? What diflFerence is there in wood of 

 different parts of the tree ? How far do climatic and soil 

 conditions influence quality ? In what respect does tapping 

 for turpentine affect quality of pine timber ? 



It is also proposed to test, as opportunity is afforded, the 

 influence of continued service upon the strength of structural 

 material, as, for instance, of members in bridge construction 

 of known length of service. This series of tests will give 

 more definite information for the use of inspectors of struc- 

 tures. 



There are four departments necessary to carry on the work 

 as at present organized, namely: the collecting department, 

 the department of mechanical tests, the department of physi- 

 cal and microscopic examination of the test material, the 

 department of compilation and Snal discussion of results. 



The collection of the test material is done by experts (Dr. 

 Charles Mohr of Mobile, Ala., for southern timbers). The 

 trees of each species are taken from a number of localities of 

 different soil and climatic conditions. From each site five 

 trees of each species are cut up into logs and disks, each 

 piece being carefully marked, so as to indicate exactly its 

 position in the tree; four trees are chosen as representative of 

 the average growth, the fifth or " check tree " the best devel- 

 oped specimen of the site. 



Disks of a few young trees, as well as of limbwood, are 

 also collected for biological study. The disk pieces are eight 

 inches in height and contain the heart and sapwood of the 

 tree from the north to the south side of the periphery. From 

 fifty to seventy disk pieces and from ten to fifteen logs are 

 thus collected for each species. and site. 



A full account of the conditions of soil, climate, aspect, 

 measurements, and determinable history of tree and forest 

 growth in general accompanies the collection from each 

 site. 



The disks are sent, wrapped in heavy paper, to the Botani- 

 cal Laboratory of the University of Michigan, at Ann Arbor 

 (Mr. F. Roth, in charge), to bs studied as to their physical 

 properties, their macroscopic and microscopic structure, rate 

 of growth, etc. Here are determined, (a) the specific weight 

 by a hygrometric method; (b) the amount of water and the 

 rate of its loss by drying in relation to shrinkage; (c) the 

 structural differences of the different pieces, especially as to 

 the distribution of spring and summerwood, strong and weak 

 cells, open vessels, medullary rays, etc. ; [d) the rate of growth 

 and other biological facts which may lead to the finding of 

 relations between physical appearance, conditions of growth, 

 and mechanical properties. The material thus studied is 

 preserved for further examinations and tests as may appear 

 desirable, the history of each piece being fully known and 

 recorded. 



The logs are shipped to the St. Louis Test Laboratory, in 

 charge of Professor J. B. Johnson. They are stenciled off 

 for sawing and each stick marked with dies, corresponding 

 to .'■ketch in the record, so as to be perfectly identified as to 

 number of tree, and thereby its origin, and as to position in 

 tree. After sawing to size, the test-pieces are stacked to await 

 the testing. One half of every log will be tested green, the 



