20 TECHNICAL PB0PEBTIB8 OF WOOD. 



dried or seasoned, that is to say, it must have lost all the moisture 

 it can part with under free exposure to air in the ordinary state. 

 The quantity of moisture in fresh-cut -wood depends on the season 

 of felling, the portion of the tree from which it is derived, and the 

 species to which it belongs. 



The rapidity and completeness with which any piece of wood 

 becomes seasoned depends on its structure, on the extent of sur- 

 face it exposes to the air in proportion to its volume, on whether 

 it is heart or sap wood, on whether it is barked or not, on the 

 quantity of moisture it originally contains, and very largely on 

 the condition of the air, especially as regards its humidity and 

 movement. Porous woods season more quickly and more com- 

 pletely than woods with a close grain. The wood of all species 

 parts with its moisture most quickly from a transverse section, and 

 least so from a longitudinal section made at right angles to the 

 medullary rays. Sapwood dries quicker than heartwood, and 

 fresh cut wood sooner than wood that has been kept sometime 

 and prevented from seasoning, moreover, wood loses its moisture 

 most rapidly just after it has been cut, the rapidity diminishing in 

 geometrical proportion with lapse of time. Wood that has been 

 previously dried and then soaked in water dries more quickly 

 and completely than wood that has been put into water green, 

 and generally the original moisture of the wood is evaporated from 

 it less slowly than the water it may take up after the tree has been 

 felled ; hence wood that has been floated or kept in water some 

 time, or, which comes to the same thing, that has been constantly 

 washed by heavy showers of rain, seasons more quickly and com- 

 pletely than wood allowed to season only under exposure to air. 

 In a damp or cold atmosphere, seasoning is slower than in a dry 

 or warm one, and very much slower in a close confined place than 

 in one in which there is a free and active circulation of air. 

 Steaming hastens seasoning, whereas impregnation with diiferent 

 solid substances retards it. The most completely seasoned wood 

 always contains from 15 to 20 per cent, of moisture, while wood 

 seasoned only in the forest contains up to 25 and even more per 

 cent. Some woods may become completely seasoned in a single 

 year, while others, such as sdl, may take more than 10 years. For 

 trades such as that of the joiner and cabinet-maker, turner and 

 cooper, wood has to be kept for two, three and even more years 

 before it can be used. 



Absorption of moisture. — The very same circumstances which 

 favour rapidity and completeness of seasoning, also favour the 

 rapidity with which a wood absorbs moisture, whether from the 



