MIKINKAUE AND STIIENOTII OF WOOD. 



79 



till" other after being soaked (or three inoiit lis in .•ohl water. The results ..f these tests on White 

 Pine arc embodied in the following- table: 



Striniilh nf mntiijiKniH hlovka of the same, ■■'canlling of U'lilU: Pine, aeUct material, in comprvasion endwise. 



[Diineu.sioiis generally, 2.70 liy 2.70 hy 2.78 iiichex.) 



a Dried at 180^ F. (to about 2 per cent moisture) before testing. 



It appears that in the tests on dry material the greatest ditterence between any two contiguous 

 blocks of select quarter-sawed White Pine was 100 pounds per sipiaic inch, or 3..S per cent of the 

 total streiiiith; that generally it was less than 2 per cent, and several times ouly about 0.2 per 

 cent, but tiiat in tests of this kind less then 200 pounds in the results can not be regarded as any 

 difference at all, this amount being due to indeterminable ditferenccs found even in the best 

 material, and partly duo also to imperfections in the means and methods of testing. It is also 

 clcnr that in the same scantling, though select and of small dimension (only C feet long) a 

 diifereiice of nearly 900 pounds per square inch, or 18 per cent of the strength, in compression 

 endwise may bo found, so that any inferences from scantling to scantling must be taken with 

 great caution, and any accurate relations, such as the influence of seasoning, etc., can be made 

 only in a manner similar to that employed in these uniformity tests. 



From the general .series of tests, also i'roni the tests on the select 2 by 2 inch pieces, and in 

 way of indication also from some of the tests in maximum uniformity, it appears that seasoning 

 affects the wood of White Pine to about the same degree as that of other pines. The strength of 

 greenwood, or wood soaked to a point where additional immersion no longer changes the volume, 

 is independent of differences in moisture. This is quite clear from the test in uniformity of the 

 scanning inriiersed for three months. Though the blocks dilfered (especially near the ends) 

 within wide limits as to tlio amount of moisture they contained, yet the strength was found to be 

 as uniform as in evenly dried timber. By drying gi'een or fully saturated wood to about 2 jier cent 

 moi.stuio (kiln drying at 80'^ C), the strength is more than doubled; and even if pieces well air- 

 dried arc kiln-dried the strength is still increased by over 10 percent. For timber to boused 

 under cover and kept properly ventilated, it is safe to presume that the strength, once seasoned, 

 will be 50 per cent greater than when green, and if used in heated rooms, an increase of 100 per 

 c(!nt on the strength of the green timber may reasonably be expected. The diagram (fig. 18) well 

 illustrates this feature. 



