Nos. 1-6. Dr. George Wilson. 7-8. Dr. J. H. Gibbon, U.S. Mint. 9-10. Professor Davy. 11-18. Dr. Pearson, _Philosoph. Trans._ 1796. 19-24. J. A. Philips, _Mém. Chem. Soc._, iv. p. 288. 25, 26. Dr. Donovan, _Chem. Gazette_, 1850, p. 176. 27-38. Mr. J. W. Mallet, _Transactions R. I. A._ vol. xxii. p. 325. 39. Mongez, _Mém. de l’Institut_. 40. Dr. E. Macadam, _Proceed. S. A. Scot._ viii. 300. In No. 31 is also Cobalt, ·09; in No. 37, Antimony, ·04; and in No. 41, Arsenic, ·03. From the varied results which so many analyses disclose, ranging as they do from 79 to 98 per cent. of copper; as well as from the diversity of the ingredients: it is abundantly obvious that no greater uniformity is traceable, than might be expected to result from the operations of isolated metallurgists, very partially acquainted with the chemical properties of the standard alloy, and guided for the most part by the experience derived from successive results of their manufacture. It is thus apparent that the various exigencies of the metallurgist, under the control of a very ordinary amount of practical skill, would lead to the determination of the best proportions for this useful alloy; though it would only be after the accumulated fruits of isolated experiment had been combined, that anything more than some crude approximation to the best composition of bronze would be determined. Hence the value of analytical evidence in determining the degree of civilisation of Mexico and Peru, as indicated by their metallurgic arts. For the general requirements of a tool, or weapon of war, where a sufficient hardness must be obtained without any great liability to fracture, the best proportions proved to be about 90 per cent. of copper to 10 of tin; or with a small proportion of lead in lieu of part of the tin: which, as further experience taught the primitive worker in bronze, communicates to the cutting instrument a greater degree of toughness, and consequently diminishes its liability to fracture. But where great hardness is the chief requisite, as in certain engraving, carving, and gem-cutting tools, the mere increase of tin in the alloy supplies the requisite quality: until the excessive brittleness of the product gives warning that the true limit has been exceeded. In this, I doubt not, lies the whole secret of Mexican and Peruvian metallurgy, which has seemed so mysterious, and therefore so marvellous to the most sagacious inquirers. The following table furnishes the results of analyses of various ancient American bronzes. Few as the examples are, they afford definite illustration of the subject under review, and supply some means of comparison with the data already furnished relative to the ancient bronzes of Europe. ANALYSES OF ANCIENT AMERICAN BRONZES.