unsuccessful. The matter of what kind of , binding material
to use is largely determined by the locality in which the bri
quettes are made, that material being used which is cheapest
and best in the locality in question, For instance, in India
and other warm climates, lime and meal mixed have proved
the cheapest and most suitable binding material; while in
the northern counties, pitch and tar are the chief ones used.
The process of making briquettes is in brief, as follows,
--The coal must first be cleaned, which is done by thorough.
washing, after which the coal is drained and dryed in special
drying ovens. The next step is to crush the coal to a uni
form size, mually about 3-16 or !A inches in diameter. The
binding material, pitch for example, may be used in the dry
state, or first melted and then mixed with the coal. When
pitch is used, it is mixed with about 15 per cent. of tar. The
ways of melting the pitch are many, but the following is a
common process and the one employed at theßlanzy, colliery,
France,—the pitch after being broken in a small pug mill, is
put,into large cylindrical tanks which are heated by steam.
The tar is then put in with hand vessels, and the melted
product is allowed to flow from a small trap door in the bot
tom of the tank. By this process 6 tons of pitch are melted
in from 6to 8 hours. The next step is mixing the prepared
coal with the binding material, the amount of the latter
varying from 6 to 10 per cent. according to the quality of the
coal. After mixing, the final process is compressing the
mixture into briquettes. The machines for this purpose
are of as many kinds as the binding materials, and usually
bear the name of their inventor. The primary features of
these machines are,—a number of moulds into which the
mixture is poured, and an apparatus for compressing each
mould to any desired. pressure. At the Blanzy colliery,
France, the briquettes are subjected to a pressure of from
142 to 156 lbs. to the square inch, and the briquetting ma
chine at this colliery turns out 23 briquettes per minute.
After leaving the machine, the briquettes are allowed to dry