SHHINKAUE AND STRENGTH OF WUOU. 



79 



tbe other after being soaked for three moutlis iu cold water. The results of these tests on White 

 Pine are embodied iu the following' table: 



Kin Ill/Ill nf cn)iti(jiioii8 lilochs iif the same scaiitltii,;! of White Pine, edict material, in viimpreasicn endn'ise. 



[Diniensious gwiefally, 2.76 by 2.7U \>y 2.70 iiiclies.J 



a Dried .it ISOJ F. (to iibout 2 pc 



out moisture) before testing 



It appears that iu the tests on dry material the greatest differeuce between any two contiguous 

 blocks of select quarter-sawed White'l'ine was 100 pounds per S(juare iueh, or 3.S i)er cent of the 

 total strength ; that generally it was less than 2 per cent, and several times only about O.i' i)er 

 cent, but that iu tests of this kind less then 200 pounds in the results can uot be regarded as any 

 difl'ereuce at all, this amount being due to indeterminable difterences found even in the best 

 material, and partly duo also to iini)erfections iu the means and methods of testing. It is also 

 clear that in the same scautliug, though select and of su)all dimension (only feet long) a 

 difterence of nearly 900 pounds per squai-e inch, or 18 per cent of the strength, in eomi>ressiou 

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

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

 only in a manner similar to that emploj'cd iu these uniformity tests. 



From the general series of tests, also from 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 froni the test in uniformity of the 

 scantling immersed for three months. Though the blocks differed (especially near the ends) 

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

 as uniform as in evenly dried timber. By drying green or fully saturated wood to about 2 per cent 

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

 dried are kiln-dried the strength is still increased by over -10 per cent. For timber to be used 

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

 will be 50 per cent greater than when green, aiul if used in heated rooms, an increase of 100 \^ev 

 cent on the strength of the green timber may reasonably be expected. The diagram (lig. 18) well 

 illustrates this feature. 



