4 



cox. 



Table II. 



Date. 



E.x- 

 posed. 



Per cent of moisture. 



Bacauan. 



Pototan. 



Air-dried. » 



Dried at 105°. 



Air-dried.' 



Dried at 105°. 



1909. 



Days. 



A. 



B. 



A. 



B. 



A. 



B. 



A. 



B. 



Jan. 7 







11.21 



11.40 



0.0 



0.0 



13.00 



13.24 



0.0 



0.0 



Jan. 29 



22 



11.23 



11.31 



10.33 



10.28 



12.43 



12.41 



10.79 



10.73 



Feb. 25 



49 



10.82 





10.00 





12.42 





10.74 





" This specimen was from the trunk of a tree 10 centimeters in diameter, and was 

 collected on August 29, 1908. About November 1, when it arrived in my laboratory, 

 it contained an amount of moisture equal to 33.07 per cent of the weight of the wood. 

 On December 17, when it was sawed to secure the above sample, it contained 22.81 per 

 cent. It was air-dried until December 29, when it contained 9.9 per cent, and was further 

 air-dried until this experiment was begun. 



* On December 17, 1908, when this sample was sawed from the specimen, it contained 

 an amount of moisture equal to 21.86 per cent of the weight of the wood. It was air- 

 dried until December 29, when it contained 11.53 per cent, and again air-dried until 

 January 7, 1910, when this experiment was begun. 



It will be noticed that tlie moisture content of both of the above air-dried 

 samples was less on December 29 than at any subsequent time, owing to a 

 diminution of the humidity on the 28th and 29th to 76.8 and 76.6 per cent, 

 respectively. The evaporation under shelter was 3.2 and 2.5 millimeters, re- 

 spectively, on those days with an average of 2.1 millimeters for the month.' The 

 relative humidity on January 7 was 81.5 and on January 29 was 80.9, with 

 an average of 80.8 for the month." During the ten days previous to February 

 25 the samples were shut in a tight room the relative humidity of which was 

 but slightly lower than that of January 29. 



The above experiment demonstrates that some change takes place 

 during the drying at 105° that prevents the wood from regaining as much 

 moisture from the air as it retains by air-drying. The amount of moisture 

 still fluctuates with the humidity of the air, but the sample thus prepared 

 always contains somewhat less than the air-dried one. 



One of the most disturbing factors in the estimation of the value of 

 a wood for fuel is the variable amount of water contained in it. It is a 

 well-knovni fact that a specimen of air-dried wood always retains an 

 amount of the water which was present in the green wood, the ultimate 

 amoimt depending upon the atmosphere which surrounds it. It takes 

 up water from or gives off water to the air imtil it reaches an equilibrium. 



Rumford '^ found in Europe that sawdust on the average contained an amount 

 of water in summer equal to about 9.3 per cent, in the autumn equal to about 

 12.3 per cent, and in the winter equal to about 19.6 per cent of the weight 



'Bull. P. I. Weathei- Bur. (1908), 484. 



^"Loc. cit. (1909), 12. 



"Nordlinger, H., Technische Eigenschaften der Holzer, Stuttgart (1860), 113. 



