Mr. T. Griffiths on Charcoal. 



265 



detailed in the following tables ; the first of which shews the spe- 

 cific gravity of the different woods. The second table shews the 

 proportion of charcoal in one hundred parts of the respective 

 woods. 



In the third table the specific gravity of the charcoal is taken in 

 the following manner. Its weight was taken in air, with its surface 

 slightly varnished, which, when it was weighed in water, prevented 

 that fluid from filling its pores. But this method not giving the 

 true specific gravity of the charcoal as its pores were filled with 

 air, another was adopted, in which the charcoal having been 

 weighed in air was put at the botton of a glass of water under an 

 exhausted receiver where it remained several hours till the air it 

 contained was expelled. Upon removing the receiver the charcoal 

 was saturated with water by the pressure of the atmosphere upon 

 its surface. In this state it was weighed in water ; the specific 

 gravities obtained by this method are given in the fourth table. 



In regard to electrical conducting power, charcoal from satin 

 wood is the best, and charcoal from tulip wood the worst. The 

 other specimens discharge a battery with nearly equal energy. 



TABLE 1. 



Lignum Vita? 1.342 



Cocoas wood 1.336 



Ebony 1.226 



Brazil wood 1.132 



Satin wood 1.078 



Tulip wood 1.070 



King wood 1.069 



Botany Bay wood .... 1.067 



TABLE 2. 



Ebony 30.5 



Botany Bay wood 28.1 



Brazil wood 26 



Cocoas wood 22.5 



King wood 22 



Tulip wood 20.8 



Satin wood 20.7 



Lignum Vitoe 17.5 



TABLE 3. 



Lignum Vitee 0.94 



Ebony 0.93 



Cocoas wood 0.86 



Tulip wood 0.76 



Botany Bay wood .... 0.57 



Satin wood 0.55 



King wood 0.7 



Brazil wood 0.6 



TABLE 4. 



Lignum Vitse 1.84 



Cocoas wood 1.36 



Satin wood 1.26 



Tulip wood 1.17 



Botany Bay wood . . . . 1.12 



King wood 1.04 



Ebony 1.4 



Brazil wood 0.84 



