HERACLIUS ON SOFTENING GEMS. 355
the
whole of the bright shining howl; which being done, I essayed to
engrave upon the glass with the hard stone known by the name of Pyrites.
" Of the engraving in Precious Stones.—Whoso
desires to attack with the steel the noblo gems which the princes of
the Roman city, they who formerly occupied her lofty palaces, loved far
above gold, let him receive, for it is extremely precious, a device
which I have discovered by deep thought. I got myself uricia (urina ?), and also blood from a big he-goat^ fed upon grass for a moderate time : which being done, with the hot blood* I engraved the gems, according as the author Pliny directs—and
" How Stones are engraved.—Take
a he-goat that has never paired, and put him in a cask for three days.
Afterwards you must kill or bleed the goat, and mix his blood with his
urine, and so steep the stone in it for one night ; and afterwards
either press it into a shape, or carve it as you please. In order to
make it beautiful (i. e. to polish it) make yourself a plate of
lead, and.sprinkle this with white flint ground small like pepper, and
rub the stone upon it until you have smoothed down its roughness. Then
tie up some of the same pounded flint in a woollen cloth, and rub
therewith the corners you were unable to get at with the leaden plate.
Then that the stone may recover its original lustre, get walnut-oil,
and rub it therewith. Furthermore you must rub it with a waxed cloth,
so that it may shine, and cease sweating.
" Sow Crystal may be engraved.—Take
crystal and wrap it up in a linen cloth steeped in the sweat of a
she-goat, and then cover it up with the cloth itself in cow-dung, and
so cut it with a knife as you may wish, but yet with
* "Calel'acto sanguine," judging from the context, should be "cale-factus sanguine," the gem being heated or boiled in the blood.
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