THE PHYSICAL PROPERTIES OF THE WOODS 

 OP THE UNITED STATES. 



The various processes by which the physical properties of the woods of 

 the United States were determined by Mr. Sharpies, in connection with 

 the Census investigation, are fully set forth in Vol. IX. of the final 

 Reports of the Tenth Census. This volume may not be accessible to all 

 persons who may have occasion to use the following tables, and the 

 methods therefore adopted in attaining these results are here briefly 

 described. 



The specific gravity, ash, and fuel value of the wood of every indige- 

 nous arborescent species of the United States, with seven unimportant 

 exceptions, were determined. The specific gravity was obtained by 

 weighing carefully measured specimens, 100 millimetres long and about 

 35 millimetres square, previously subjected to a temperature of 100° C. 

 until their weight became constant. The ash is given in percentages of 

 the dry wood, and was determined by burning small blocks of the wood 

 in a muffle furnace at a low temperature. 



The relative approximate fuel value of any wood is obtained by 

 deducting its percentage of ash from its specific gravity ; and the cor- 

 rectness of the result thus obtained is based upon the hypothesis first 

 proposed by Count Rumford, that the value of equal weights of all 

 woods for fuel is the same. It would be more correct, however, to say 

 that the fuel value of the organic matter in all woods is approximately 

 the same. 



Wood is made up of two factors, — organic matter, composed of car- 

 bon, hydrogen, and oxygen, with a small amount of nitrogen, and a still 

 smaller amount of sulphur; and inorganic or mineral matter, — ash, as it 

 is generally called, — without value as fuel. The specific gravity represents 

 the weight of equal volumes of wood ; and if from the specific gravity the 

 weight of the ash, which varies greatly in different species, is deducted, 



