the others, for which reason crystals take the first place. From these, whei.
pounded, the most excellent transparent glass was made in India, with which
no other could be compared, as Pliny relates. The second place is accorded
to stones which, although not so hard as crystal, are yet just as white and
transparent. The third is given to white stones, which are not transparent.
It is necessary, however, first of all to heat all these, and afterward they are
subjected to the pestle in order to break and crush them into coarse sand,
and then they are passed through a sieve. If this kind of coarse or fine sand
is found by the glass-makers near the mouth of a river, it saves them much
labour in burning and crushing. As regards the solidified juices, the first
place is given to soda ; the second to white and translucent rock-salt ; the third
to salts which are made from lye, from the ashes of the musk ivy, or from
other salty herbs. Yet there are some who give to this latter, and not to the
former, the second place. One part of coarse or fine sand made from fusible
stones should be mixed with two parts of soda or of rock-salt or of herb
salts, to which are added minute particles of magnes.19 It is true that in our
