( 546 ) 
The V. life. 
The laft ufe, I lhall now mention of our Inftrument in re- 
fereoce to Metals , is , that it may aflift us to eftimate the qua- 
lity of Metalline Mixtures, whether in Coins or other MaflTes, 
and to guefs at the proportion of the Ingredients that com- 
pofe them. For, fince we have formerly fecn, that th^ fame 
Inftrument , employed to examine Guinys , Tervcd alfo for 
Crown-pieces of Silver that wanted of an Ounce lefs than a 
twenriech part of that weight , 'twill be eafily granted , that 
the fame inftrument, and more eafily , that a larger one, may 
be fo fitted, as to help Goldfmiths , Chymifts and others, 
that are not acquainted with Hydroftaticks , to make fuch an 
eftimate as will not much deceive them of the finenefs of 
Gold and its differing Allays with Silver or fome other deter- 
minate Metal, 
In order to this, the Inftrument may be fitted to fink to fhe 
tip of the Pipe with fome determinate weight of the fineft 
Gold, as of 24 Carats, as they call that which is moft 
pure and fine. But 'twill be convenient , that this Metal , 
in the Air, be juft an Ounce, or half an Ounce, or fonve 
fuch determinate weight , that is commodioufly divifibfc into 
many aliquot parts. Then you may make a mixture that con- 
tains a known proportion of the metal whei-^with -you allay 
the Gold 5 as if it hold 19 or 15 parts of Gold, and one of 
Silver; and, letting the Inftrument fettle in the Water, mark 
the place where the Surface of the Water cuts the ftem orpipe. 
And then putting-in an other mixture, wherein the Silver has a 
new and greater proportion to the Gold ; as if the former be 
'an eighteenth or a fourteenth part of the later, you may ob* 
ferve, how much Icfs than before this depreffes the Inftru- 
ment, and fo you may proceed with as many mixtures or de- 
grees of Allays as you think fit, or can be diftinguifhed con- 
veniently on the ftem 7 being alwayes careful , that, whatever 
be 
