er embodyed together, of that which hath both been put into
the cupp together, and the silver alone in these where it was put alone
in the leaden case. And to part the silver and the gold in the first
experiment, they put the mixed body into a glass of aqua-fortis, which
separates them by spitting out the silver into such small parts that you
cannot tell what it becomes, but turns into the very water and leaves
the gold at the bottom clear of itself, with the silver wholly spit out,
and yet the gold in the form that it was doubled together in when it was
a mixed body of gold and silver, which is a great mystery; and after all
this is done to get the silver together out of the water is as strange.
But the nature of the assay is thus: the piece of gold that goes into
the furnace twelve ounces, if it comes out again eleven ounces, and the
piece of silver which goes in twelve and comes out again eleven and two
pennyweight, are just of the alloy of the standard of England. If it
comes out, either of them, either the gold above eleven, as very fine
will sometimes within very little of what it went in, or the silver
above eleven and two pennyweight, as that also will sometimes come out
eleven and ten penny weight or more, they are so much above the goodness
of the standard, and so they know what proportion of worse gold and
silver to put to such a quantity of the bullion to bring it to the exact
standard. And on the contrary, [if] it comes out lighter, then such a
weight is beneath the standard, and so requires such a proportion of
fine metal to be put to the bullion to bring it to the standard, and
this is the difference of good and bad, better and worse than the
standard, and also the difference of standards, that of Seville being
the best and that of Mexico worst, and I think they said none but
Seville is better than ours.

2. They melt it into long plates, which, if the mould do take ayre, then
the plate is not of an equal heaviness in every part of it, as it often
falls out.

3. They draw these plates between rollers to bring them to an even
thickness all along and every plate of the same thickness, and it is
very strange how the drawing it twice easily between the rollers will
make it as hot as fire, yet cannot touch it.

4. They bring it to another pair of rollers, which they call adjusting
it, which bring it to a greater exactness in its thickness than the
first could be.

5. They cut them into round pieces, which