are now called after the Greek name ceratia ; and each double sextula is
divided into four semi-sextulae, which are called granas ; and each semi-sextula
is divided into three units of four siliquae each, of which each unit is called
a grenlin. If we made the needles to be each four siliquae, there would be
two hundred and eighty-eight in a bes, but if each were made to be a semi-sextula
or a double scripula, then there would be ninety-six in a bes. By these two
methods too many needles would be made, and the majority of them, by reason
of the small difference in the proportion of the gold, would indicate nothing,
therefore it is advisable to make them each of a double sextula ; in this wa>
twenty-four needles are made, of which the first is made of twenty-three
duellae of silver and one of gold. Fannius is our authority that the Ancients
called the double sextula a duella. When a bar of silver is rubbed on the
touchstone and colours it just as this needle does, it contains one duella of gold.
In this manner we determine by the other needles what proportion of gold
there is, or when the gold exceeds the silver in weight, what proportion of
silver.
