The traditional account of so recent a discovery as that of Galvani, is the preparation of frog soup for his wife, and the accidental touching one of them with the knife; while, in fact, he had been for years employed in examining the convulsive action of frogs, and had presented several memoirs to the Institute of Bologna on the subject, before its general publicity; indeed, in the main fact he had been anticipated by Swammerdam, and he possibly by others. Schwartz, the monk of Cologne, probably had a real existence, probably had something to do with the progress of pyrotechnic art; it is even more probable that he invented gunpowder than that the public invented him. The very accident which is reported to have happened, it is not altogether improbable did happen; but if a mixture of saltpetre, sulphur, and charcoal accidentally exploded, it was not accident which brought together those particular three ingredients out of the whole laboratory of nature and art. It is indeed possible that the frequency of accidental explosions when gunpowder was known, 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 Bibliothèque 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.