estion is that it is connected
with "chirk" or "chark," an old word meaning "to make a grating noise."

_Wood-charcoal._--In districts where there is an abundance of wood, as
in the forests of France, Austria and Sweden, the operation of
charcoal-burning is of the crudest description. The method, which dates
back to a very remote period, generally consists in piling billets of
wood on their ends so as to form a conical pile, openings being left at
the bottom to admit air, with a central shaft to serve as a flue. The
whole is covered with turf of moistened soil. The firing is begun at the
bottom of the flue, and gradually spreads outwards and upwards. The
success of the operation--both as to the intrinsic value of the product
and its amount--depends upon the rate of the combustion. Under average
conditions, 100 parts of wood yield about 60 parts by volume, or 25
parts by weight, of charcoal. The modern process of carbonizing
wood--either in small pieces or as sawdust--in cast iron retorts is
extensively practised where wood is scarce, and also by reason of the
recovery of valuable by-products (wood spirit, pyroligneous acid,
wood-tar), which the process permits. The question of the temperature of
the carbonization is important; according to J. Percy, wood becomes
brown at 220 deg. C., a deep brown-black after some time at 280 deg.,
and an easily powdered mass at 310 deg. Charcoal made at 300 deg. is
brown, soft and friable, and readily inflames at 380 deg.; made at
higher temperatures it is hard and brittle, and does not fire until
heated to about 700 deg. One of the most important applications of
wood-charcoal is as a constituent of gunpowder (q.v.). It is also used
in metallurgical operations as a reducing agent, but its application has
been diminished by the introduction of coke, anthracite smalls, &c. A
limited quantity is made up into the form of drawing crayons; but the
greatest amount is used as a fuel.

The porosity of wood-charcoal explains why it floats on the surface of
water, although it is actually denser, its specific gravity being about
1.5. The porosity also explains the property of absorbing gases and
vapours; at ordinary temperatures ammonia and cyanogen are most readily
taken up; and Sir James Dewar has utilized this property for the
preparation of high vacua at low temperatures. This character is
commercially applied in the use of wood-charcoal as a disinfectant. The
fetid gases produced by the putre