, the stack, when
formed, being covered with a thick layer of dung, to protect it from the
dissolving action of the rain. In the winter, this fuel is conveyed to
Kounboum, and there sold.

The luxurious variety of combustibles which the civilized nations of
Europe enjoy, have exempted us from the necessity of making any very
profound researches into the divers qualities of argols. Such has not
been the case with the shepherd and nomadic peoples. Long experience has
enabled them to classify argols, with a perspicuity of appreciation which
leaves nothing to be desired in that particular respect. They have
established four grand divisions, to which future generations will
scarcely be able to apply any modification.

In the first rank are placed the argols of goats and sheep; a glutinous
substance that enters largely into its composition, communicates to this
combustible an elevation of temperature that is truly astonishing. The
Thibetians and Tartars use it in the preparation of metals; a bar of
iron, placed in a fire of these argols, is soon brought to white heat.
The residuum deposited by the argols of goats and sheep after combustion,
is a sort of green vitreous matter, transparent, and brittle as glass,
which forms a mass full of cavities and very light; in many respects,
closely resembling pumice stone. You don't find in this residuum any ash
whatever, unless the combustion has been mixed with foreign matter. The
argols of camels constitute the second class; they burn easily, and throw
out a fine flame, but the heat they communicate is less vivid and less
intense than that given by the preceding. The reason of this difference
is, that they contain in combination a smaller proportion of glutinous
substance. The third class comprehends the argols appertaining to the
bovine species; these, when thoroughly dry, burn readily, and produce no
smoke whatever. This is almost the only fuel you find in Tartary and
Thibet. Last come the argols of horses and other animals of that family.
These argols not having, like the others, undergone the process of
rumination, present nothing but a mass of straw more or less triturated;
they throw out a great smoke when burning, and are almost immediately
consumed. They are useful, however, for lighting a fire, filling the
office of tinder and paper to the other combustibles.

We perfectly understand that this rapid and incomplete essay on argols is
not of a character to interes