[ i8i 1 



Let this be weighed f ; its weight will ferve to find the fpecific 

 gravity of the foil ; for if 96 ciibic inches weigh n pounds, 1728 

 (a cubic foot) fhould weigh x pounds, and x divided by 75,954- 

 will exprefs by the quotient the fpecific gravity of the foil. 

 To render this and the fubfequent operations more intelligible I 

 fhall illuftrate each by an example : Suppofe the 96 cubic inches 

 to wei?h 6,66 pounds, then 1728 cubic inches fhould weigh. 



1 20 lb. and -=1,579. 



75=954- 



2°- The earth being weighed is next to be broken down and' 

 freed from all ftony fubftances above the fize of a pippin, and 

 the remainder well mixed together to render the whole as homo- 

 geneous as poflible ; then weigh the ftones that were picked out, 

 and find the proportion belonging to each pound of the refiduary 

 earth ; call this the ftony fupplcment, and denote it by S. — Thus 

 if the ftones weigh ilb.= i2 0z. the remainder or mere earth muft. 

 weigh 5,661b. and if to 5,661b. there belong i2ozs. of ftone,, 

 to I lb. muft belong 2,12014025. or 2 ozs. 57,66 grs.= 1017,66 grs. 

 This then is the ftony fupplement of each fucceeding pound=6'. 



3°- Of the earth thus freed from ftony matter take lib. — S. 

 (that is the above cafe ilb. — 2 oz. 57ygrs.) heat it nearly to. 

 rednefs in a flat veftTel, often flirring it for half an hour, and 

 weigh it again when cold. Its lofs of weight will indicate the 



quantity 



f Troy weights are generally more exaflly made than avoirdupois, and therefore fhould be 

 preferred. A cubic foot of pure water weighs 75,954 troy, very nearly, or 62,5 avoirdupois, 

 pounds, at the temperature 62°. 



