THE MODERN MICROSCOPE.* IN this handsome volume of three hundred
and eighty-two pages, we have a most elaborate treatise on the microscope and its mechanism. Dr. Van Heurck, the author, is an enthusiast on the subject, which has occupied much of his attention from childhood, and the present work is practically the fifth edition of a book which has already passed through four editions on the Continent. Every department of science has now grown so extensive that if a book is thorough, it must be restricted to narrow limits ; and this is the case in the pre- sent instance. The introduction commences at the very be- ginning of the subject,—with elementary optics; the properties of light, and the nature of reflection and refraction ; and then passes on to discuss the various kinds of lenses, and their combinations and applications to the simple and compound microscope. Subsequently the author, and Mr. J. W. Stephen- son, discuss Dr. Abbe's theory of microscopic vision, by which the effects of diffraction in distorting images of microscopic objects can he calculated and corrected.
The author then proceeds to describe the essential parts of the microscope, commencing with the objectives, at which point he intercalates a section on tests. His own specialty is the group of Diatomaceic ; and the few allusions to the prac- tical, as apart from the theoretical, use of the microscope, which we find in other parts of his work, relate almost exclu- sively to Diatoms ; but here he discusses a variety of test objects, both natural and artificial. Among the latter we notice Nobert's tests, which consist of a series of very fine parallel lines ruled on glass. We regret to note that "the tests, or proof tables as Nobert called them, are truly wonderful, and nothing was known up to his death of the process employed by this maker in tracing lines so fine, and so clear." This is not as it should be. Surely, no one is justified in allowing any discovery or invention to die with him. Even if he does not choose to allow others to share in it during his own life-time, he might leave the details behind him to be made known after his death.
The oculars (or eye-pieces, as they are often termed), the stage, movements, and illuminating and accessory apparatus are then described, followed by a general account of simple and projection microscopes. In the next chapter, we find sections on the situation and arrangement of the work-room, choice of light, magnification, hygienic rules for microscopical research, example of a microscopical observation, and choice of a microscope. In the course of his remarks, the author takes occasion to correct what he considers two popular fallacies : (1), that the higher the magnifying power, the better observa- tions can be made; and (2), that the use of the microscope is injurious to the eyesight. Every one who has had the least experience with a microscope knows that it is never desirable to employ higher magnifying powers than are absolutely re- quired for the work on hand ; while, as regards the second point, Dr. Van Heurck argues that the use of the microscope is by no means injurious to the sight, if only ordinary care be taken. The next hundred pages are occupied with an elaborate description, fully illustrated, of the microscopes produced by the best English, French, German, and American makers, among which English makers figure very prominently, though the firm of Carl Zeiss, of Jena, is perhaps more often referred to than any other throughout the book.
The remainder of the work consists of chapters on the measurement and reproduction of microscopical objects, photo- micrography (probably one of the most useful sections in the book), cause of errors in microscopical observations, preservation of the microscope (one of the rules laid down being that no one must touch the instrument but its owner), general rules for preparing microscopical ob- jects, the microscopist's library, and the microscope in the past and in the future. And now, how far does the work before us answer the requirements of a general monograph
on the microscope P There can be no question that it will be of great value to professional microscopists, and to those who make a special study of the microscope as a scientific instru- ment, and these advanced students will no doubt benefit TiteMinvoseops as Construction and Management, including Toohnigne, Photo. Micrography, and the Past and Future of the Mtutimoope. By Dr. He Van Hourok, Profeesor of Botany, and Director at the Antwerp Botanical Gardens ; late President of the Belgian Microscopical Society ; Hon. FALLS. and New York MS. English Edition, re-edited and augmented by the Author from the Fourth French Edition, and translated by Wynne E. Baxter, F.B.M.S • F.G.S. With three Platen, and upwards of 250 Illustrations. London Crosby Look.
wood and Son. New York: D. Van Noatrand Company. nes. largely by its contents. But the amateur would only be bewildered by the number of instruments and appliances recommended, and might even be led to abandon the idea of microscopie study as hopelessly difficult and complicated, and ruinously expensive. The author has probably kept in view his favourite Diatoms throughout ; but we should have pre- ferred a book in which special chapters had been devoted to the best means of applying the microscope to special investi- gations, from such simple objects as hair, scales, and Fora- minifera on the one hand, to Bacteria, &a, on the other. Another chapter which would have been useful and interest- ing, might have been devoted to the hand-lenses so much used in England for botanical and entomological purposes, such as the Stanhope and Coddington ; but these are not even mentioned. The chapter on the leading microscopes of the day might certainly have been very greatly curtailed, if not wholly omitted. It reads like an optician's sale- catalogue ; it cannot be complete, for there must be many other makers of first-class microscopes in various countries besides those mentioned; and at the best it can only be of temporary value, for alterations in the firms themselves, and improvements or modifications in the instruments which they manufacture, must soon render this part of the book of merely historical interest. It seems to us to usurp valuable space which might have been put to much better account.
The printing, paper, and illustrations of the book are excel- lent ; but we notice a few misprints, owing, perhaps, to the book being a translation,—such as " lena " and " Jena " for Jena, though the last form also occurs. Dr. Van Heurck's portrait forms the frontispiece, and we are informed that his work on the Diatomaccie of Belgium is being prepared for translation into English, and will be published uniformly with the present work, to which it is intended to be supplementary.
We will terminate our notice of the present work on the microscope by again expressing our opinion that while it will be invaluable to advanced students, it will be found far too elaborate on the one hand, and far too restricted in its range on the other, for the requirements of beginners or amateurs.
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