of 11 parts of oxygen mixture--a suitable quantity for all coals
exported--would enable operators to obtain similar figures, and make the
test uniform in different hands.

The following is a brief outline of the method of procedure recommended:
Sample the coal until an average portion passes through a sieve having
64 meshes to the square inch. Take about 300 grains (20 grammes) of this
and run through a brass wire gauze having 4,600 meshes to the square
inch, taking care that the whole sample selected is thus treated. One
part of nitrate of potash and 3 parts of chlorate of potash (dry) are
separately ground in a mortar, and repeatedly sifted through another
wire gauze sieve, having 1,000 meshes to the square inch, in order that
the oxygen mixture shall _not_ be ground to an impalpable powder, as
this is very undesirable. It absorbs moisture rapidly, and interferes
with the regularity of the combustion when very fine. 330 grains of the
powder are weighed out (after drying), and intimately incorporated
with 30 grains of coal--better with a spatula than by rubbing in a
mortar--and then introduced into a copper cylinder (31/2 inches long by 3/4
inch wide, made from a copper tube), and pressed down in small portions
by a test-tube with such firmness as is required by the nature of the
coal, not tapped on the bottom, since the rougher portions of the oxygen
mixture rise to the surface. As the temperature of a room is almost
invariably much higher than the water supply, a little hot water is
added to that placed in the glass cylinder, until the difference of
temperature between the water and the room is about the mark indicated
in the following table:

Room at The water should be

80 deg. F. 70 deg. F.