EDGE TOOLS are treated of under the head Cutlery.
ELECTRUM or German Silver. - See Silver, Albata, and Brass. The respective modes being used, according to the nature of the works made in this triple alloy, which differs greatly as to value and quality.
ELVANS, the modes of working and polishing porphyry and granite, and also the elvans, which are of intermediate character between these two, are described in pages 169 to 172 of the first volume. By the lapidary, the elvans and porphyries are wrought like Carnelian, the granite somewhat differently, on account of its unequal hardness, see Granite.
EMERALDS. - These valuable stones, the finest of which are found in Peru, are considered to be very soft gems, and in consequence they require more than ordinary care in their polishing, and still do not admit of such acute angles and edges being given to them as to many of the harder gems. The Emerald is worked just like Carnelian.
ACETS, a few words are given on the cutting of the facets or gems at the con-elusion of the article on Carnelian, but the subject will be considered more at length in the chapter on lapidary work.
FAYRER'S SWING HONE. - This is a flat and parallel slip of brass, in form like a hone, but with pivots at the ends by which it is suspended in two notches, so that this metal lap, or factitious hone, may accommodate itself to the angle at which the razor or other instrument is applied to it. The one side of the brass is first used with fine oilstone powder and oil, afterwards the second side with pulverised water of ayr stone and oil, and the razor strop is afterwards resorted to, see Trans. Soc. of Arts, vol. 48, p. 248.
FELSPAR. - The fine varieties of this siliceous mineral, display most beautiful and varied iridescent colours; namely, blues and greens in the Labrador Felspar, a beautiful apple green in the Amazon Stone, and a pearly white in the Adularia or Moonstone, the colours are best seen when the specimens are polished, which is effected as with Carnelian although Felspar is scarcely so hard.
FISH SKIN is the skin of the Dog Fish, and some others which is dried as its only preparation. The scales of the skin are hard and pointed and stand up obliquely, so that they cut or abrade very effectually in the one direction, but not in the other. Fish skin is more durable but less generally convenient than glass paper, to which it probably gave rise. It is however now but little used in polishing, although in clearing off rounded and irregular works, as in pattern making, from the fish skin being somewhat rigid, when bent round the finger it may be almost used as a file, and it has the further advantage of leaving nothing behind it, whereas, glass paper commonly deposits some of the particles of glass in the surface of the wood, to the detriment of any tools subsequently employed. The fins should be selected for fine works.