The extant works of Geber are, for the most part, in Latin, and are all open to more or less legitimate suspicion. In the library at Leyden there are said to be several Arabic manuscripts which have never been translated, and there is one in the Imperial Library at Paris, together with a _Fragmentum de Triangulis Sphæricis_ which is still unprinted. The most complete edition of Geber is that of Dantzich, published in 1682, and reproduced in the Collection of Mangetus.[F] First in importance among the works of the Arabian adept must be ranked his “Sum of Perfection”--_Summæ Perfectionis magisterii in suâ naturâ Libri IV._ The next in value is the treatise entitled _De Investigatione perfectionis Metallorum_, with his Testament, and a tract on the construction of furnaces. * * * * * The “Sum of Perfection, or the Perfect Magistery,” claims to be a compilation from the works of the ancients, but with the doubtful exception of pseudo-Hermes, we are acquainted with no alchemical authors previous to the supposed period of Geber. A knowledge of natural principles is declared to be necessary to success in the art. The natural principles in the work of nature are a potent spirit, and a living or dry water. The disposition of the philosophical furnace and of the _vas philosophorum_ is clearly described; the latter is a round glass vessel with a flat round bottom, and has several elaborate arrangements. A marginal note, however, declares that the account of it is hard to be understood. Among all the obscurities of the treatise, it is absolutely plain that it is concerned with metals and minerals. The properties of sulphur, mercury, arsenick, gold, silver, lead, tin, copper, iron, magnesia, lut, marchasite, are discussed in such a manner that it is impossible to establish an allegory, or to interpret the words of the writer in other than a physical sense. FOOTNOTES: [F] J. J. Mangeti, “Bib. Chem. Curiosa,” 2 v. fol. 1702. RHASIS.