THE WORLD'S MINERALS.
The World's Minerals, By Leonard J. Spencer, M.A. (W. and R. Chambers. 5s.)—Mr. Spencer's book, with its excellent coloured illustrations—there are forty plates commonly containing each four figures, and some with more—is likely to be a most useful volume. A popular account of these substances in general, their formation, character, &c., is followed by a special account of the various groups into which they are divided. Thus we have "the Native Elements" (non-metallic, semi-metallic, and metallic), the sulphides, oxides, carbonates, sulphates, &c., phosphates, &c., sili- cates—this last consisting of eight groups—and titano-silicates. A final chapter deals with substances—amber, coal, &c.—which are really organic. Of each of these a description is given, and the substance itself, as we have said, effectively pictured on the opposite page. Pitch blonde and autunite are distinguished by containing radium. But the first of these, though the more fertile of this wonderful substance, does not give more than ono grain for nearly half a ton.—With this may ho mentioned Tha Diamond, by W. R. Cattolle. (John Lane. 7s. Od. net.)—This volume is intended to assist in giving to the jewellery trade and the public a comprehensive and intelligible account of the information extant about precious stones. Wo may explain that the author has already in previous works dealt with other parts of this subject, as with precious stones in general and with the pearl. It is natural that a separate volume should be given to the diamond. It is the acknowledged head of the class. It has qualities in which it is unrivalled, it has greater intrinsic value, ,and it is a larger factor in the commerce of the world. AU these branches of the subject are treated with satisfactory fullness by Mr. Calton's, who has given us a highly interesting and useful book. The history of the gem and of particular specimens of it, the places where it is found, the processes by which it is made available, its uses, and—a very strange chapter—the attempts, genuine or fraudulent, to manufacture it, arc to be found here. It is always rash to prophesy when the matter concerned is part of the great struggle of man with nature, but the conditions of the problem seem to make any effective manufacture of the diamond unlikely, so great are the forces which have to be employed. It is true that real diamonds have been made, but these are very small. The largest diamond over made was less than one millimetre across. (A millimetre is about the twenty-fifth part of an inch.) If a larger one could by any moans be brought into existence it would be likely to explode.
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