and on the Nature of the Diamond. 219 



While fir - - 300 grains. 

 Lrignum vitae - 800 grains. 

 Box - - 400 



Beech - - 500 

 EngHsh Oak - 230 

 Mahogany - 200 



These slips were put into small crucibles, and completely 

 covered with dry sand. Heat was very gradually applied at 

 first, until the volatile parts were dissipated ; they were thea 

 kept about 40 minutes in a white heat. On being collected 

 and weighed, while still warm, the charcoal from each was 

 as follows : 



54*5 grs. equal to 181" 7 per cent. 

 17-25 

 20-25 

 15 



17-40 



13-75 

 These being exposed to/ the air during one week, increased 

 n weight thus : 



Fir - - - 13 percent. 



Lignum vitse - 9*6 



Box - - - 14 



Beech - - 16-3 



Oak - - - 16-5 



Mahogany •• 18 



Certain quantities being confined in common air increased 

 very little in weight, and all in the same proportion ; we are 

 therefore much inclined to think that this increase is owing 

 to an absorption of water from the air j and we repeatedly 

 found that the greatest increase of weight took place in the 

 first hour or two after exposure, and arrived at its maximum 

 in less than 24 hours, as the following experiment, selected 

 from several others, will prove. 



40 grains of charcoal from willow wood, which had been 

 put into a bottle with a ground glass stopper immediately 

 after they were removed from th^ fire, were exposed in the 

 scale of a delicate balance, in a room where the thermo- 

 meter was 62° Fahrenheit, barometer 30- 2C. 



C 6 o'clock 



