, were reflected back as a plausible hypothesis to
account for its invention; but as the explosive power and utility of
gunpowder were not facts which could have been arrived at by _a priori_
reasoning, there is every likelihood of such an accident having
originally suggested the application of an explosive mixture as a means
of propulsion. The history of the invention then resolves itself into
the question, Were any admixtures of these three ingredients previously
known, what led to them, and what were the objects proposed by them?
This question is attempted to be answered by the book before us,
containing a very erudite inquiry into the progress of the invention of
Greek fire and gunpowder, which are, according to the author's view,
modifications of the same thing, _i.e._ pyrotechnic compositions,
differing only or mainly in the proportions or purity of their
ingredients. A mass of very curious information is given to the reader,
which, in addition to the general stock of knowledge or obscure
tradition on this subject, shows a gradual and generally diffused use of
sulphur, saltpetre, and charcoal in different proportions, and
occasionally mixed with other combustible substances. Among the Arabs of
the thirteenth century a vast number of receipts for such mixtures
existed; this is proved by some ancient Arabic MSS. preserved in the
Bibliotheque Royale. How the Arabs got possession of these arts is left
somewhat in obscurity, though our authors consider there are strong
grounds for conjecturing that they obtained then originally from the
Chinese about the ninth century; that they then proceeded slowly in
improving this knowledge for the three centuries during which they had
no intercourse with the Chinese; and that they again acquired further
information on these points after the Mongul irruption in the thirteenth
century.

The defect of the book before us is its inconclusiveness: from the
preface we are led to expect the solution of a theorem; after reading
the book through, we find ourselves not indeed as far at sea as ever,
but aided mainly by negations. The actual origin of gunpowder or Greek
fire is not traced; many of the connecting links in the chain of
pyrotechnic discovery are still deficient; and the conjectures, which
stand in the place of conclusions, are frequently founded upon what
appear to us insufficient data. On the other hand it must be admitted,
that on a subject so involved in obscurity, inasmuch as