THE AUSTRIAN YELLOW. 231
was able to cleave off protuberances at a blow.
The
accompanying diagrams represent a certain large diamond both in the
rough and after it was cut into a brilliant, and they will help to
explain the process of diamond-cutting, which is briefly as follows:
The first process is to make lead models of the stone in its actual
state and also in the ideal, namely, after it is cut. By this means is
found out the most economical way to shape it. The next step is to
cleave it toward that shape as far as possible. Cleaving is performed
in two ways; by a steel saw strung on a whalebone and coated with
diamond dust which saws off the required amount; or by scratching a
nick with a diamond point in the direction of the grain and splitting
it off with one blow. This latter process, observes an old writer,
requires great strength of mind as well as dexterity of hand, for by an
unlucky blow a valuable stone may be utterly ruined. Supposing however
that the cleavage has been
