ter distance through the colored mass, and more of the light, of
color other than that of the stone, is absorbed.

IMPROVING COLOR BY PROPER CUTTING. In addition to the color improvement
that can be brought about by changing the shape of the cut stone there
are a number of gem materials whose color varies very greatly in
different directions, and this fact calls for skillful use in order to
obtain the best possible results. Thus most tourmalines of deep color
must be cut with the top or table, of the finished stone, on the _side_
of the prismatic crystal rather than at right angles to the axis of the
prism. If cut the latter way they would be much too dense in color. On
the other hand, most blue sapphires should be cut _across_ the prism
axis rather than the way that tourmalines should be cut. To cut a
sapphire with its table on the side of the prism would be likely to
cause it to have a greenish cast because of the admixture of the
unpleasing "ordinary ray" of yellowish tint with the blue of the stone
as seen up and down the prism. Some Australian sapphires are of a
pronounced green when viewed across the axis of the crystal.

Rubies if cut, as was recommended for sapphires, give a very pure and
very deep red color, but lack somewhat in the display of dichroism given
by rubies that are cut with the table on the side of the crystal and
parallel to its axis. Lapidaries need to know and to make use of such
optical relations as these and jewelers might well inform themselves in
such matters, especially if they have, or hope to acquire, trade in very
fine colored stones.

EFFECT OF SHAPE ON BRILLIANCY. In actual practice it is common to find
colored stones poorly cut for brilliancy, especially central
brilliancy, and that, too, without the excuse of sacrifice of brilliancy
in order to improve color. The fault is usually due to too great a
desire to save size and weight. Frequently a stone would have greater
value if properly cut, even at the expense of some size and weight. When
stones are cut too shallow, as is frequently the case, they are sure to
leak light in the center and they are thus weak and less brilliant there
than they would be if made smaller in diameter and with steeper back
slopes approximating 44 degrees.

Round stones, if their angles are correct, are more brilliant than
stones of other contour such as square or cushion shape, or navette or
heart shape. It can readily be seen that such odd-shaped stones