Page:Popular Science Monthly Volume 39.djvu/578

578 expressing it. He treats also of that exaggeration of spontaneous attention known as surprise or astonishment. The chapter upon voluntary attention makes up the greater portion of the volume. The study of natural attention enables him to inquire into the genesis and mechanism of voluntary attention, and to arrive at some comprehension of it. He concludes the chapter with the statement that attention in no respect resembles an independent activity; that it is bound up with perfectly determined physical conditions, that it acts only through the latter, and is dependent on the same. The last chapter treats of morbid states of attention. The name of the author is a guarantee that the work is both interesting and instructive.

The word "System" in the above title has especial significance. It indicates that the treatise to which it is applied is characterized by a methodical arrangement. Taking the periodic classification of the elements as a basis, the author has undertaken to bring into the field of inorganic chemistry an orderly arrangement similar to that which has prevailed for more than twenty years among the compounds of carbon. This, he says, owing to traditional and commercial influences, has not been done before in any book written in English. After a short historical introduction the elements are considered in order, and within a moderate compass. Next their compounds with the halogens are taken up. The author names as a defect of many previous books the ignoring of the double halides, except in a few special instances; accordingly, he has taken pains to have these compounds well represented. The oxides, sulphides, selenides, and tellurides follow next, "double oxides, such as sulphates, for example, being considered among the compounds of the simple oxides with the oxides of other elements." Other features of previous books which Prof. Ramsay has aimed to avoid are magnifying the difference and obscuring the relationship between acid hydroxides and basic hydroxides, neglecting the borides, nitrides, etc., and giving pre-eminence to methods of preparing compounds which are of commercial utility over other methods which have fully as much scientific importance. After the account of the oxides, a few chapters are occupied with the borides, carbides, and silicides, and the nitrides, phosphides, arsenides, and antimonides; and in these the organo-metallic compounds, the double compounds of ammonia, and the cyanides are considered; while a short account is given of alloys and amalgams. "The chemistry of the rare earths, which must at present be relegated to a suspense account, is treated along with spectrum analysis in a special chapter; and the systematic portion of the book concludes with an account of the periodic table." The concluding part of the volume deals with manufacturing processes, which are so grouped that substances generally manufactured under one roof are treated together. In regard to the adaptability of his system to teaching the author says: "Having used it for four years, I am perfectly satisfied with the results. For the student, memory work is lightened; for the teacher, the long, tedious description of metals and their salts is avoided; and I have found that the student's interest is retained, owing to the fact that all the 'fire-works' are not displayed at the beginning of the course, but are distributed pretty evenly throughout."

extended and practical book is due to a State law directing the Geologist to make examinations and reports in regard to economic products. The first part of the volume describes the distribution and geology of the iron ores of Minnesota so far as they are known. These comprise magnetites, hematites, and some limonites. Next the methods of exploration and mining that are employed in the State are described, and accounts are given of the principal mines. There is a chapter on the facilities for transporting and marketing the Minnesota ores, another on the origin of the deposits described in the first part of the report, and a