Page:Popular Science Monthly Volume 30.djvu/726

704 a brief bibliography, and the book ends with a good index.

beauty in any mineral that may be found in Nature is accompanied by a corresponding rarity of the same, so that possession for ornamental purposes is only possible to those having wealth or power, the material belongs to the class of precious stones. Although precious stones are not indispensable to the world's progress, they flatter human vanity, and have therefore a not unimportant place in human affairs. The large money value a precious stone represents compared with its volume, rendered this sort of property valuable in former times as an additional medium in commercial interchange; the perfected banking methods of the present day have, however, relegated precious stones to their proper field—adornment and as curiosities.

The author does not discuss the usefulness of precious stones. Since they are used, have been always used, and are a very important article of commerce and industry, he tells us all he knows about them or has been able to gather from other authors; origin, properties, classification, prices, trade, pawns, sumptuary laws, size, collections, crown-jewels, secular and sacred uses, their place in literature, mystical properties, and engraving on precious stones. Many historical facts are given which make the book very readable and interesting. The above subjects arc distributed in the first nine chapters. The following chapters are devoted to the description and histories of the different varieties of precious stones. Among these the diamond occupies the first place. In two chapters the history, home, mining, trade, polishing, etc., of the diamond are minutely given, accompanied by much historical information. Another is devoted to historical and remarkable diamonds. The history of each of these stones—or as much as is known—is given in each case. The record is not what would be considered the best part of human nature. Murder, wars, artifice, theft, plunder, and treachery are the jewels on which the larger number of these remarkable diamonds are set, and very few of these historical diamonds have a clean history. The largest diamond known is the Braganza,or King of Portugal, weighing from sixteen hundred and eighty to eighteen hundred and eighty carats uncut, the genuineness of which is, however, doubted. There are two, the Matan and Nizam, weighing over three hundred carats, uncut, and seven, four of which are cut diamonds, weighing between two and three hundred carats. The diamond loses about one third of its weight by cutting.

The diamond is pure crystallized carbon. The stones which belong to the class of the precious corundum, which is supposed to be nearly pure alumina, are the most valuable after the diamond. They are sapphire, asteria, emerald, amethyst, topaz, and ruby.

The beryl class includes several varieties: the emerald, acquamarines, and topaz, which, to distinguish them from those of the corundum species, are termed Occidental, while these are termed Oriental. The difference in composition is that the beryl species contain silica and other substances besides alumina. Opals and pearls: spinet, garnet, tourmaline, turquoise, lapis-lazuli, chrysolite, chrys-oberyl, iolite, kyanitc, apophyllite, labradorite, and other gems, and the crystals of the quartz family, are described in the last four chapters.

There are six appendices, giving the size of the largest diamonds; classification of precious stones according to their constituents; hardness, and specific gravity, and relative hardness, relative specific gravity, localities in the United States where gem-minerals have been found.

present number is unusually rich. The leading article is by Professor William James, of Harvard University, entitled "The Perception of Space." Professor Henry Sidgwick writes a criticism upon Dr. Martineau's ethics, and James Ward, author of the article upon psychology in the new edition of the "Encyclopædia Britannica," replies to some comments of Professor Bain upon his work. J. M. Cattell, Ph. D., contributes an account of some interesting experiments on the association of ideas. Five critical notices by Professor A. Seth,