INFLUENCE OF MOISTURE ON STUENQTII. 



19 



INFLUENCE OF MOISTURE. 



This influence is among the most important, hence all tests have been made with due regard 

 to moisture contents. Seasoned wood is stronger than green and moist wood; the ditlereuce between 

 green and seasoned wood may amount to 50 and even 100 per cent. The influence of seasoning 

 consists in (1) bringing by means of shrinkage about 10 per cent more fibers into tlie same square 

 inch of cross section than are contained in the wet wood; (li) shrinking the cell wall itself by about 

 50 per cent of its cross section and thus hardening it, just as a cowskiu becomes thinner and 

 harder by drying. 



In the following tables and diagram this is fully illustrated; the values presented in these 

 tables and diagrams are based on large numbers of tests and are fairly safe for ordinary use. They 

 still require further revision, since the relations to density, etc., have had to be neglected in this 

 study. 



Jnjhieiice of iiinistiire on sirenijth. 



Dending strength : 



(Ireon 



]l:ilt' ilry 



Yard dry 



Kcjoni dry 



Cruehing endwise: 



Green , 



Half dry 



Yard dry 



Koorii dry 



Mean ut' both bending and enj«hing strength: 



Green 



Half dry 



Yard dry 



Boom dry 



Per 

 cent of 

 mois- 

 ture. 



3^+ 

 20 

 15 

 10 



33 + 

 20 

 15 

 10 



33+ 



20 



15 



10 



Average of all valid tests. 



c-"-- "CI 



8,450 



10. U50 



11, 950 

 15, 30U 



5,000 

 6.600 

 7,850 

 9, 200 



7,060 

 8,900 

 10, 900 

 14, 000 



4,450 

 5,450 

 6, 850 

 ',), 200 



Lob- 

 lolly. 



7,370 

 8, 050 

 10, 100 

 12, 400 



4,170 

 5,350 

 6,500 

 8,650 



Short- 

 leaf. 



6,900 

 8,170 

 9,230 

 11, 000 



4,160 

 5,100 

 5,900 

 7,000 



Kelative values. 



Cuban. 



100 

 118 

 142 

 181 



100 

 132 

 157 

 184 



100 

 125 

 149 

 182 



Long- 

 leaf. 



100 

 116 

 142 

 182 



100 

 122 

 1,54 

 206 



100 

 Hi) 

 148 

 194 



Lob- 

 lolly. 



100 

 117 

 138 

 168 



156 



200 



100 

 122 

 147 

 187 



Short- 

 leaf. 



100 

 118 

 134 

 160 



100 

 122 

 142 

 168 



100 

 120 

 138 

 164 



Aver- 

 age. 



100 

 117 

 139 

 173 



100 

 126 

 152 

 191 



100 

 122 

 146 

 182 



4 S & 7 S S 



Fia. 3 — Uia^'ram showing variation of compression strength with uioiaturo. 



It will be observed that the strength increases by about 50 per cent in ordinary good yard 

 seasoning, and that it can be increased about 30 per cent more by complete seasoning in kiln or 

 house. 



Large timbers require several years before even the yard-seasoned condition is attained, but 

 2-inch and lighter material is generally not used with more than 15 per cent of moisture. 



