temperature
is elevated. When a projectile force is necessary, a further condition
is essential, viz., that they liberate by their chemical action gaseous
matter, whereby a sudden increase in volume is produced, the expansion
of which, augmented by the high temperature, produces the required
effect of propulsion.

This slight sketch will show that the purity and proportions of the
saltpetre, and the inflammable substances mixed with it, are the main
elements to be attended to in the improvement of self-burning
compositions: it is indeed far from improbable, that the substances used
in purifying saltpetre have first suggested such compounds. Wood ashes
were used at a very early period for purifying nitre; and at the end of
an Arabic receipt of the thirteenth century, for the preparation of
saltpetre, in which charcoal is used, is the expression, "guard against
sparks of fire."

The probabilities strongly favour the view, that incendiary compositions
of the nature we have been describing originated with the Chinese. China
snow, and China salt, are the names given by writers of the greatest
antiquity to saltpetre. In the Arabic MSS. to which we shall presently
allude, the words Chinese wheel, Chinese flower, Chinese dart, occur as
appellatives of different fireworks. It is very possible that the influx
of Chinese literature, which the result of the recent war with that
people promises us, will lead to the discovery of Chinese treatises upon
pyrotechny.

Other authors speak of fire-arms among the Chinese at a very early
period of our era, and even before Christ; but the interpretation which
they have put upon obscure passages--interpretations evidently derived
from their existing knowledge--makes these expressions and translations
of extremely doubtful import.

At a later period, however, we have the authority of Raschideddin,
(minister of the Tartar Khan of Persia,) and of Marco Polo, that the
machines of war employed at the siege of Siang Yang were constructed by
Arabian or European workmen, and that the Tartars were not at this
period themselves able to manufacture such machines. This would tend to
negative the belief which has been entertained by some, that the Chinese
then used gunpowder as a means of projection, but does not lessen the
possibility that the fuses and compositions projected by these machines
were of Chinese origin.

In the history of the dynasty of Sang, A.D. 1259, there is a distinct
account of