FROM WOOD AND COAI 37 



The bushel generally used in this country contMns 2150.4 



cubic inches, but as coals arc sold by what is termed "rounded 

 measure," or partially heaped, it became necessary to ascertain 

 the cubical content of a body of coal thus measured. For this 

 purpose one bushel of charcoal was made perfectly dry. and tin 

 mean specific gravity of a large Dumber of pieces was found 

 to be .285, and the weigh! of the bushel of coal was fifteen 

 pounds avoirdupois, or 105000 grains, and the absolute w< ighl 

 of a cubic foot of coal whose specific gravity is . Js~>. is 1 1 n;87 

 grains, and a cubie foot being 1728 cubic inehes, then wehavethi 

 following statement: As 124687: 1728: : 105000: I 155 solid 

 inches of coal in the bushel, which being known, tin absoluti 

 weight of a bushel of each of the coals was calculated from 

 their specific gravities, in the following manner: 



The weight of a cubic foot, or 1728 cubic inches of any 

 substance, whose specific gravity is 1. being 1000 OUUCCE 

 consequently the weight in ounces of a bushel containing l 155 

 cubic inches of any substance, of the same specific gravity, will 

 he found by the following proportion : 



V~ 1728:1000 :: 1455 : 842 = 52.62 pom,!-. 



Now to find the weight of a bushel of a SUbstanci of an\ 

 other specific gravity, we say: As unify is to (52.8 1) the weight 

 of a bushel at specific gravitj t,so la the given specific gravity. 

 to the weight of a bushel at that specific gravity. Thus foi 

 white ash charcoal, we have, As 1 : 52.62::. 547: 28.78po Is 



From a number of comparisons, made by actual measure 

 ment, of different mineral coals, it is believed the weights <\ 

 pressed in the table will be found sufficiently correcl iii even 

 instance. 



The hydrostatic balance made use of to asa rtain the specific 

 gravities of the different bodies expressed in the table, is .,n. 

 sibly affected by ,.'; part of a grain, when not loaded, ami tin 



Weights wire made to twentieth parts of < grain in i\' i\ in 



stance. 



From experiments mad< to ascertain tin w< ighl of moistun 

 absorbed b\ tic differenl woods, which had previousrj been 



VOL. HI. — k 



