( 348 ) 
otherwife, in their opinion, it might in due time be brought 
to. 
Perhaps it may not be amifs on this occafion to add as an Im- 
provement of this fifth life of our Inttrument , that it may be 
employed to examine other mixtures befides allay 'd Coins, 
and that , if the Inftrument be adjufted to an Ounce, for in- 
ftance, of pure Copper, it may help men to make an ellimat 
of the Alloy of Tinn, or the quantity of it that is oftentimes 
added to Copper , to make differing forts of Bell-metal , and 
ofthofc metalline^Sjp^^W^ , whether plain or concave, that are 
caird -Steel-glaflTes, as alfoof Soders confiding of certain pro- 
portions of Silver and Brafs, or Copper 5 in all which, and di- 
vers others,thedifcovery of the proportion of the Ingfedients 
may, on fome occafions, be ufeful to Tradefmen, as well as 
defirable by Virtuofi. And though I have obferved, that, by 
mixture, Tinn and Copper acquire a fpecific gravity fomwhat 
differing from v^hat their Ingredients promife 5 yet,fince the In- 
ftrument is to be fitted for fuch eftimates, not by calculation, but 
by tryals, the eftimates may be made rear enough to the 
Truth. 
