INTRODUCTION. 19 



we can — since we know its true specific gravity is i"56 

 — determine tiie cubic contents of the solid substance : 

 it is j^g =: 22*43 cubic centimeters. That is to say, of 

 the 100 cubic centimeters total volume of the fresh piece 

 of wood, 22'43 cubic centimeters were solid substance, 

 and therefore 77'S7 cubic centimeters were cavities, and 

 in these cavities (if we assume that no other spaces 

 exist) the 50 grams — i.e. 50 cubic centimeters — of water 

 were distributed. 



This would imply that 77'S7 — 50 (= 27-57) cubic 

 centimeters were occupied with air or other gases. 



But the assumption that all the water must be con- 

 tained in the cavities is found to be erroneous, for it 

 turns out that a portion of it is taken up into the solid 

 substance of the wood itself, and is there held with 

 peculiar tenacity. It is this imbibed water, in fact 

 which it is so difBcult to get rid of, even at high tempe- 

 ratures, and which never is expelled in the ordinary 

 process of drying, or " seasoning," wood. It is measured 

 by the following method. A piece of the wood is dried 

 thoroughly at 1 10° C, and its volume and weight deter- 

 mined ; a thin transverse slice is selected, because it 

 cracks radially as it dries. The thoroughly dried, 

 cracked slice of wood is now hung in a moist atmosphere, 

 kept at a suitable temperature, for several days. Here 

 it absorbs and condenses some of the water, and the 

 crack closes up tight. When it is found that no more 

 water is thus absorbed, the piece of wood is again 

 carefully weighed and measured and examined, and it 

 is found that although there is no liquid water in the 

 cavities, the increase in weight is considerable. 



Now, since the volume of the wood-substance was 

 known — by dividing the dry weight by the specific 

 gravity v$6 — it is possible to determine the relations 



c 2 



