< 343 ) 
isfufpefled to be counterfeit ; adding a graia-weighc or two of 
Gold in cafe the propofed Coin needs it ; I fay, z grain-vpeight 
of Gold, becaufe, if it be of Brafi, of which the grain weighty 
coniinonly ufed, are made, it will loofe in Water more than i t 
fhould of the weight it had in the Air ; and therefore it will be 
ufcful to fuch as intend to try feveral forts oiEngliJh Coins, as 
Angels, Tm and twenty jhillingpieces^doMe Guwys^^cc. to have 
by them a numerous fet of grains, (about whofe fhape, by the 
way^ one need not be curious,that not being material) made of a 
thin plate of fterling Gold. 
The III. Ufe. 
If the Inftrument be skilfully fitted for fuch a purpofe.it may 
be mide to ferve to examine fome fores of white money lefs 
heavy than half Crowns. And becaufe it may be ufeful to 
know in general what Coins may, and what may not, be ex. 
amin'd by this or that particular Inftrument proposed , i 
ftall here add a general way that is not difficult for finding 
this out; namely ^r/?, by weighing the piece of Gold or Sil- 
ver in the Air, and afterwards in the Water, and fubftraflmg 
the latter from the former, to obtain the difference of the two 
weights: k^d^next^ by weighing alfo in the Air and in the 
Water a piece of Copper, or Brafs, if this be the likelyeQ-to 
be employed in counterfeiting the Coin, and obferving like- 
wife tl)e difference between thofe weights. For, theleflerof 
thefe differences being fubftraded from the greater, the re- 
mains will fhew, how much the true piece of Coin will out- 
weigh the other in the water, and confequently if fo many 
grains, as this refidue amounts to, being added to the weight 
of the lighter metal , do make a fufficiently manifeft deprefll. 
on of it below the Mark it would ftay at without that addi- 
tion, one may probably conclude , that the difference be- 
tween a true and counterfeit piece of Coin propos'd, will be 
difcoverable by the Inftrument. 
The 
