TIMBER PHYSICS UNIFORMITY OF STRENGTH. 



369 



In addition, the dilliculty of seasoning oak without defects or even securing perfect material may have influenced 

 the results of tests so as to cloud the relationship with the genus. 



If further close study, supplemented by additional series of tests carefully devised to investigate this relation- 

 ship, should uphold the truth of it, this result may be set down as the most important practical one that could lie 

 reached by these, tests, for it would at, once give into the hands of the wood consumer a means of determining the 

 relative value of his material as to strength and all allied properties by a simple process of weighing the dry material; 

 of course with due regard to the other disturbing factors like crossgrain, defects, coarseness of grain, etc. 



Itesults of tfsl.t in miiii>i-fHnii,n n<-ross grain (a) and shearing with grain. 

 ; I'imnils per square inch.] 



To an indentation of :t per ''-'nt of the height of the specimen. 



b Actual tests on "dry" material not reduced for moisture. 



Having fully established the great influence of moisture on the strength of wood, the practi- 

 tioner still needed information as to the rate and manner of drying and as to the way in which 

 moisture is distributed during seasoning. Several thousand moisture determinations were made 

 and it was established beyond doubt that moisture is generally least abundant at the ends, is 

 quite evenly distributed throughout the length, but is not always uniform in different parts of the 

 same cross section, often varying in this respect within astonishing ranges, so that the use of 

 timber in a half-seasoned condition, and where uniform seasoning can not be obtained by the 

 material, requires that these facts be duly considered in designing. 



TESTS OP MAXIMUM UNIFORMITY. 



Both in this country and abroad small differences in strength values were often interpreted 

 as deciding for or against any given material. This same problem arose also in every case where 

 many results were to be compiled, and it seemed especially desirable once for all to find just how 

 much uniformity could be expected of wood materials. From a large series of well-selected 

 quarter-sawed pieces representing several kinds of pine, cypress, and hardwoods it was found 

 that even contiguous blocks, 2.} inches long, may differ by as much as 2 to 4 per cent in conifers 

 and as much as 13 per cent in oak, and that in a scantling only (i feet long the butt might differ from 

 the top by 10 to 20 per cent in conifers and over 35 per cent in oak. This extremely valuable set 

 of results throws much light upon discussions of the past, and is well suited to show that many 

 boastful claims rested on very flimsy and entirely unreliable differences, such as might well be 

 accounted for by a little more extended examination of materials. It will also assist in judging 

 test results in the future and help to avoid useless controversy and prejudice. The following 

 more fully illustrates the results of this series: 



Scantlings of air-<lry material, 6 to 10 feet long, of white pine, longleaf pine, tuliptree (poplar), and white oak, 

 and of perfectly given material of lolilolly pine and cypress, fresh from the saw, were cut partly into blocks 2 by 2 

 by 2 a r inches, but mostly into cubes of 2| inches. All material was quarter sawed, carefully prepared, and in all 

 cases treated alike, either perfectly green or dried together at the same temperature. Altogether 52!) tests in 

 endwise compressi'iu were made, namely, 100 on white pine, 72 on longleaf pine, !)9 on loblolly pine, 40 on whito 

 oak, 115 on tuliptree (poplar), 103 on cypress. 



II. Doc. 181 2i 



