Page:Popular Science Monthly Volume 6.djvu/647

Rh the true nature of as many of these minerals as possible. There is, however, a large class of minerals (the silicates, etc.) which, unless distinctly crystallized, present considerable difficulties to the field-worker. To partly overcome these difficulties, the supplementary tables were added by Prof. Weisbach, whereby, through the instrumentality of a bottle of acid, a matrass, a blow-pipe, and a couple of fluxes, a still larger number of species can be identified."

is equally well known in the scientific and business world: in the scientific world as a mathematician, physicist, and member of the Royal Society; in the business world as printer to her Majesty, and the proprietor of an immense book-manufacturing establishment. The excellent little volume which is just produced on one of the most difficult departments of optics is, in a certain sense, the product of both the activities in which the author is engaged. It consists of lectures delivered at various times to audiences of the working people in his employ. In these lectures Mr. Spottiswoode attacked the most complex part of optical science, and one which it has hitherto proved most difficult to expound satisfactorily in a book; but, by the profuse employment of experiments, the lecturer was probably able to bring the subject within the range of his listeners' comprehension—its striking phenomena, at all events, if not their completest explanation. In this little volume the text is as clear as is consistent with extreme brevity, and the numerous well-executed woodcuts are valuable helps to the understanding of the subject, and will go far to replace the experiments which were made with the instruments represented.

science of chemistry is growing into immense proportions, and with its enormous expansion there comes a revolution in its theory of so radical a nature as to bewilder the old students, and raise a serious question how the prodigious mass of facts and details is ever going to be got into any thing like rational order. But, while Theory is perplexed, Practice proceeds with but little disturbance; only, as the field extends, division of labor has to be carried farther, and the more special departments of science are increasingly cultivated. The present work appears in obedience to this tendency, and furnishes a hand-book for a branch of analysis of no small importance, and which has hitherto hardly had its proper share of attention. The author remarks in his preface:

"Proximate organic analysis is not altogether impracticable, and organic chemistry is not solely a science of synthetical operations, even at present. It is true, as the chief analytical chemists have repeatedly pointed out, that in the rapid accumulation of organic compounds, the means of their identification and separation have been left in comparative neglect. It is true, also, that the field is limitless, but this is not a reason for doing nothing in it. Fifty years ago, the workers in inorganic analysis were unprovided with a comprehensive system, but they went on exploring the mineral kingdom, and using their scanty means to gain valuable results."

but a pamphlet of 42 pages, it contains seven papers, each giving good, solid, original work on a difficult subject. Prof. Mayer has of late made acoustics a special field of investigation, and has given to science some admirable results.

document is devoted to the metallurgy of iron. It specifies six ores in Missouri; gives their respective characteristics, and tabulates the quality of the iron when produced by smelting with charcoal, and coke, or coal, for the four irons technically known as foundery-iron, mill-iron, Bessemer-iron, and steel-iron. As a contribution to economical geology, it is valuable.