berated, and well arranged manual of elementary chemistry in all
its branches. For the correctness and accuracy of its contents the name of the writer is a sufficient guarantee, holding as he does no mean rank amongst English chemists, and having given close attention not to one only, but to many branches of his subject. Small as it is, as a standard general text-book it deserves to take a leading place, and to supply the deficiencies of Fownes's Chemistry, now somewhat antiquated ; although for clearness of expression and simplicity of language Fownes's is perhaps superior. It is impossible to acquire even the scantiest knowledge of chemistry merely by attending popular lectures, without reading up to them, working out the numerical calculations, and com- mitting to memory a good many numbers and names. For this purpose this work is particularly well adapted, being very sparing of examples and illustrations, which belong more particularly to the province of a lecturer. The writing is a little stiff, like the writing of a man who has more matter on his hands than he has space and inclination to popularize and dilute with many words. Indeed, almost too much has been sacrificed to brevity. On one subject in particular, that of Spectrum Analysis, a little more detail and a few more pages of explanation and illustration would have been an improvement. The theory and method of spectrum analysis are not stated and explained so clearly and fully as they might have been, and any one previously ignorant of the subject would have some difficulty in understanding it. This highly interesting and important branch of chemistry is so newly discovered, and there is, comparatively speaking, so little to be said about it, that it might have been treated more exhaustively. Nothing is said, for instance, of the method of analysis without combustion by throwing a ray of light through a solution of the substance to be ex- amined, a process to delicate that by it the presence of human blood can be detected in the smallest shred of a blood-stained garment, though the stain may be many years old. By no previously known means can human blood, when once it is dry, be with certainty distinguished from that of other animals. This is the more remarkable, as on the subject of light Professor Roscoe is particularly well qualified to speak. He has given much attention to it, and together with Professor Bunsen, of Heidelberg, invented the Photometer, a beautiful contrivance for ascertaining the intensity of light by measuring its action in causing hydrogen and chlorine to combine. Much care has been bestowed on accuracy in the smallest details. Changes have been made in the old- fashioned nomenclature, especially of salts, with a view to make it more in accordance with the mode and principle of their combination. The old school would hardly recognize carbonate of lime, chlorate of potash, sulphate of iron, and so on, under their new names of calcium car- bonate, potassium chlorate, and ferrous sulphate. Even carbonic acid is grudged its old name, and appears generally as carbonic dioxide. No doubt the change has been rightly made, as the old nomenclature sug- gested a theory no longer believed in, or at any rate unproved. The worst of it is that it involves the necessity of remembering two names for the same thing, otherwise in practice serious mistakes would be made ; a druggist would probably be puzzled, if he were asked for potassium chlorate. A carefully prepared series of questions added in an appendix is a most useful addition to the book, and will be fully appreciated by those who wish to have their knowledge of the subject in a precise and readily producible form.
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