LXXVIII PHILOSOPHICAL SOCIETY OF WASHINGTON. 
ings made in 1820, equations (9) and (12) agree fairly well, but 
equation (5) is very discordant, as are also equations (7) and (8). 
All the evidence seems to point to an error of about one and one 
half grains in equation (5); and if instead of (5) we write ( 
R. S. Troy lb. = Exch. (8 0z. + 4 0z.) — 2 grains (5’) 
(7) will become 
Exch. (8 oz. + 4 0z.) = Mint (8 oz. + 4 oz.) — # grain (7’) 
and then all the equations will be reasonably accordant. 
