( 344 ) 
The cheapnefs of thefe flight Inftriimcnts being confider- 
ed , it may be expedient for Goldfmiths and others , that 
have frequent occafions to examine various foirts- of Coin, to 
have a feveral Inftrument adjufted for each of them, to fave 
themfelves fome pain and trouble. But if the Ball be made 
large, and fitted with a ftero flender and long enough, one 
may quickly by changing the balaft-places , as oceafion re- 
quires, fit the fame Inftrument to examine Coins of differing 
metals , and of very differing weights. For one of thefe, 
made of Copper , ferves me to examine both Guinys and 
Crown-pieces of Silver, and half Crowns too 5 and it may be 
eafily made to ferve alfo for divers forreign Coins. 
ThelV.Ufe» 
'Tis a great complaint of Pewterers , that the Tinn they buy 
of the Miners or Merchants is often adulterated with Lead , as 
they find to their prejudice when they have made Veflelsof it* 
And many others , that are Buyers , complain much more of 
divers Pewterers for putting too much Lead into their Pewter, 
becaufe Lead is by many times cheaper than Tinn. On thefe 
accounts I fliall add, to the other ufe of our Inftrument, fome- 
thing that relates to Tinn and Pewter. Though I muft take no- 
tice, that fome Tinn may perhaps be found a little heavier in 
j^^-^/g than ordinary , althotJgh no fraud intervene ; becaufe I 
haveobferv'd fome Tinn (as I elfewhere relate) to contain 
fome, though but a very little, proportion of Gold or Silver. 
But this being no ufual cafe, I fhall proceed to fay , that the 
Pewrerer may judge, whether the Miner or Merchant have de- 
ceived him • if, taking a piece of Tinn that he knows to be 
pure, and is of a convenient weight, heobferves how much it 
deprelTesthe Pipe, and then makes the like obfervation with an 
equal piece of the Tinn fu fpefted to have Lead or fome other 
Metal in it. For if this deprefles the Inftrument much lower 
than 
