JO ON THE HEAT EVOLVED 



necessary, were made at each time to this mass, from two other 

 masses of the same articles compounded, whose specific gravi- 

 ties were known to he about .995 and 1.005, the mass weighed 

 when finished more than thirty ounces, and required seven days 

 to accomplish the undertaking, and the proportions of the 

 ingredients found to have been used, were about 22 grains of 

 rosin to 100 grains of wax. Having had occasion to use some 

 of this compound within a short time, I regret to say, that the 

 lapse of two years since it was made, has produced a change 

 in its specific gravity, it being now 1.004 in water at the tem- 

 perature of 60° Fahrenheit. 



The pieces of wood being made positively dry, in the manner 

 described for drying those experimented upon, they were covered 

 with the compound described without regard to its weight, and 

 their specific gravities being ascertained, the absolute weight 

 of dry wood in a cord of each was found in the following man- 

 ner, and will be seen in the table. 



The weight of a cubic foot of any substance, whose specific 

 gravity is 1, is known to be very nearly 1000 ounces, or 62^ 

 pounds avoirdupois. Hence, to find the weight of a cord of 

 wood, or 7 1 £ cubic feet of plenum, of specific gravity 1 , (for 

 example, shell-bark hickory) we have only to multiply 71.5 

 by 62.5, which gives us 4468.75. Now, to find the weight 

 of a cord of wood, of any other specific gravity, we say, As unily 

 is to (4468.75) the weight of a cord at specific gravity 1, so is 

 the given specific gravity, to the weight of a cord at that specific 

 gravity. Thus, for white ash; 1 : 4468.75 ::. 772:3449. 87 

 pounds. In fact, we have, in any case, merely to multiply 

 4468.75 by the specific gravity of any other wood, to obtain 

 the weight of a cord of this wood, in pounds and decimals avoir- 

 dupois. 



The quantity of charcoal which can, by the best conducted 

 process, be obtained from the different woods, was deemed 

 an inquiry of considerable importance, there being great dis- 

 crepancies in the results of different experimenters on tins 

 subject, and from the vast importance and consumption of tin's 

 article in the arts generally, and particularly in the process of 

 smelting iron ore. For this purpose all attempts hitherto made 



