The section relating to the _chemical characters_ is concise, and professedly proceeds upon the principle of selection. It might perhaps have been, to some extent, advantageously enlarged; although, it is true, the author refers us to the particular minerals for individual instances; still it might have been well to have illustrated the general principles by a few well-chosen instances, _e. g._ how, by the blowpipe, _galena_ is distinguished from _sulphuret of antimony_; _carbonat of lead_ from _sulphat of barytes_, or _carbonat of lime_; _garnet_ from _titanium_; _plaster of Paris_ from _soapstone_, &c.; and, among trials in the moist way, how by nitric acid and ammonia, _iron pyrites_ is distinguished from _copper pyrites_; and how, by acids, _sulphat of lime_ is known from _carbonat of lime_. As the acids are used principally for trials on the effervescence of carbonats, most of which form with sulphuric acid, insoluble compounds, we should doubt whether sulphuric acid is so advantageously employed as the nitric or muriatic, in such cases, on account of the clogging of the effervescence by the thick magena, produced by a recently precipitated and insoluble sulphat. According to our experience, the nitric or muriatic acid, diluted with two or three parts of water, is most eligible. With respect to the blowpipe: it is _a convenience_ to have a mouth-piece of wood, or ivory, joined to a tube of metal, as Mr. Cleaveland recommends; and some authors direct to have the tube attached to a hollow ball, for the sake of condensing the moisture of the breath; but every thing which adds to the expense and complication of the instrument will tend to discourage its use; we have never found any difficulty in performing every important experiment with the common goldsmith's brass blowpipe; and are confident, that, after the learner has acquired the art, or _knack_, of propelling a continued stream of air from his mouth, by means of the muscles of the lips and cheeks, while his respiration proceeds without embarrassment through the nostrils, he will need no other instrument than the common blowpipe. Indeed it is a truly admirable instrument, instantly giving us the effect of very powerful furnaces, the heat being entirely under command, the subject of operation and all the changes in full view, and the expense and bulk of the instrument being such that every one may possess it, and carry it about his person.