rge which had
never reached the temperature necessary for reaction, and which is
altered only by the intrusion of salt from the inner part of the
furnace. Special precautions are taken in making and breaking the
intense current here used (amounting at the end to about 750 kilowatts,
or 1000 E.H.P.), a water-regulator consisting of removable iron plates
dipped in salt water being used for the purpose. In such a furnace as
that above described the charge weighs about 14 tons, the yield of
carborundum is about 3 tons, and the expenditure of energy about 3.9
kilowatt-hours (5.2 H.P.-hours) per pound of finished product. The
carborundum thus produced is crystalline, greenish, bluish or brownish
in colour, sometimes opaque, but often translucent, resisting the action
of even the strongest acids, and the action of air or of sulphur at high
temperatures. The crude product can therefore be treated with hot
sulphuric acid to purify it. In hardness it nearly equals the diamond,
and it is used for tool-grinding in the form of vitrified wheels (mixed
with powdered porcelain and iron, pressed into shape and fired in a
kiln). Carborundum paper, made like emery paper, is now largely used in
place of garnet paper in American shoe factories, and finds a market in
other directions. The amorphous carbide, which was at first a waste
product, has been tried, it is reported, with success as a lining for
steel furnaces, as it is said not to be affected by iron or iron oxide
at a white heat. (W. G. M.)

CARBOY (from the Pers. _qarabah_, a flagon), a large globular glass
vessel or bottle, encased in wicker or iron-work for protection, used
chiefly for holding vitriol, nitric acid and other corrosive liquids.

CARBUNCLE (Lat. _carbunculus_, diminutive of _carbo_, a glowing coal),
in mineralogy, a garnet (q.v.) cut with a convex surface. In medicine
the name given to an acute local inflammation of the deeper layers of
the skin, followed by sloughing. It is accompanied by great local
tension and by constitutional disturbance, and in the early stages the
pain is often extremely acute. A hard flattened swelling of a deep-red
colour is noticed on the back, face or extremities. This gradually
extends until in some instances it may become as large as a
dinner-plate. Towards the centre of the mass numerous small openings
form on the surface, from which blood and matter escape. Through these
openings a yellow slough or "core" of leathery