the Faraday Society, the Royal Microscopical Society and the Photomicrographic Society, these groups being in co6peration with the Technical Committee of the British Science Guild. A f t e r some reference to the state of the art, and reminders of the importance to both Britain and America of so cultivating the practical side that these nations may be independent of all others, the general history of the microscope is taken up. It is shown by a quotation that Seneca knew that curved surfaces will magnify, and it is stated to be probable that the manuscript illuminators of the fifteenth century were familiar with moderate magnifyfilg apparatus. The first illustrated publication which gives definite evidence of the use of a magnifying glass appeared in I592 at Frankfort, bearing the name of George Hoefnagel. It consisted of a series of plates engraved on copper illustrating common natural objects, but drawn with great skill and minute accuracy. Some of the drawings reveal details that are hardly distinguishable to the unassisted eye. A Dutchman, Zacharias, miscalled Jansen, and his son, made microscopes before the year I619. In I665, Hooke published his famous book " Micrographia," in which he described using small drops or globules of glass. A fac-simile of the title page of the book is given. A good deal of space is given to the subject of metallography, which though comparatively recent in its extensive applications, and in the efforts to construct apparatus for its pursuit, yet is really over a century old, the method having been first used by Widmanstiitten in i8o8, who polished a specimen of meteoric iron and examined the surface. His work is preserved in the title " WidmanstStten F i g u r e s " applied to the phenomenon. The.practical application of the microscope to the study of metallic masses is due to Sorby, who began his work in this line in I864. Years before, however, he had laid the foundation of one of the most important applications of microscopy--petrography--the extensive ramifications of which are now one of the most prominent features of mineralogy and geology. The book is illustrated by a large number of excellent plates and many illustrations in the text. Necessarily, being made up of the contributions of many persons and of notes of extemporaneous discussions, the subject matter is somewhat disconnected, but the material presented is all of importance and value, and the book constitutes one of the best of recent publications in the field of pure and applied microscopy. HENRY LEFFMANN. A TExT-BooK OF PRACTICAL CHEMISTRY. By G. F. Hood, M.A. ( O x o n . ) , B.Sc. (Loud.), and J. A. Carpenter, M.A. (Oxon.). xii @ 5I 4 pages and index, i62 illustrations, 8vo. Philadelphia, P. Blakiston's Son and Co. Price $5.0o net. To those whose first descriptions of laboratory manipulations were derived from Morfit's Chemical Manipulations, the contrast with the modern works in this field is sufficiently striking. The introduction of electricity and the employment of vacuum apparatus have notably modified every-day procedures. The present work is a very comprehensive description of methods in the preparation and testing of chemical compounds, covering both inorganic and organic fields. It is compactly and conveniently printed, and contains a very large amount of information, so that a student who should go through it
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carefully and conscientiously will acquire a very satisfactory knowledge of the practical procedures in chemistry, and as these procedures are explained in their theoretical relations, such student will have also a good idea of the fundamental principles of the science. Eighty-eight pages are given to physical chemistry, in which important methods are elucidated, among which may be mentioned optical activity, electro-chemistry, spectroscopy and the phase-rule. HENRY LEFFMANN. A TExT-BooK ON SURVEYING AND LEVELLING. By H. Threlfall, M.Sc. Tech., Engineering Lecturer in the College of Technology, Manchester. 663 pages, illustrations, I2mo. London, Charles Griffin and Company, and Philadelphia, J. B. Lippincott Company, 192o. The practice of surveying in this country is so different from that taught i~l England, that it is difficult to review an English work on this subject, and do justice to its author. In this country, for instance, the chain is rarely used, except by the old-time county surveyor, the modern surveyor making his measurements either with steel tape and band, or in a rough country by the stadia method; the results obtained with the latter being as accurate as chaining, and at an economy of time and labor. The use of the measuring rod for extreme accuracy, which apparently is stressed by Prof. Threlfall, has been practically abandoned in this country. Greater speed and as high a degree of accuracy is obtained by the use of steel bands, observing connections that reduce the percentage of e r r o r to such a minim u m that the methods are employed in the measurement of U. S. primary base lines. The description of the use of the Plane Table would be of little service to an American engineer, as his method and purpose in using this instrument are so radically different from those described by the author. On the other hand, the chapters treating of " Cuttings and Embankments," and the adjustments for linear errors in a closed polygon survey, without affecting the angular measurements, contain some valuable information. There is also a v e r y excellent chapter on " Photographic S u r v e y i n g " and the chapter on " Tacheometry," or as it is commonly called in this country, " Stadia Surveying," is complete and practical. BENJAMIN FRANKLIN. LABORATORY MANUAL FOR TIlE DETECTION OF POISONS. By Wilhelm Autenrieth, University of F r e i b u r g i.B. Authorized translation by William H. \Varren, Ph.D. F i f t h American edition, 322 pages, contents, index and 25 illustrations, 8vo. Philadelphia, P. Blakiston's Son and Co. Price $3.5 o. This work has been s o long before the chemical profession that it needs little more than a notice of the appearance of a new edition. It is a translation from the fourth German edition, the same as was used in the preparation of the fourth American edition, inasmuch as a revision of the German work has apparently not yet appeared. T h e r e is also a special British edition, in which some subjects not found in the German original were included and are also treated in the American edition. A m o n g these is the vexing question of