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GEIKIE, LORD LISTER, Prof. CANNIZZARO, Prof. VON KÖLLIKER, Prof. S. NEWCOMB, Sir W. HUGGINS, LORD RAYLEIGH, Prof. SUESS, and Sir WM. CROOKES belong to a New Series and are Photogravures. Proof impressions of any of the above, printed on India paper, may be had from the Publishers, price 5s. each; or the Series of 36 Portraits in a Handsome Portfolio for £9 5s., carriage paid. The Portfolio may be had separately, price 6s. Cheques and Money Orders payable to MACMILLAN & CO., Ltd. OFFICE OF "NATURE," ST. MARTIN'S STREET, LONDON, W.C. 46 Hatton Garden, London, E.C. CONSTANT DEVELOPMENT NEW SHOW ROOM.-The finest in England. Having removed our Workshops and Test Rooms to larger Factory at 9 & 10 Bentinck Mews, W., we have been enabled to devote a very large room to a display of all that is latest and best in X-Ray and Electro-Medical Apparatus. THOROUGH DEMONSTRATIONS GIVEN ANY TIME OF THE DAY. "EARTH-FREE MULTOSTAT" UNIVERSAL APPARATUS. All currents quite Independent of main. No possibility of Earth Shocks. Provides Galvanic, Sinusoidal, Galvano-Sinusoidal currents, Cautery, and Light. Motor for Drills, Vibrators, Pumps, &c., and for Intermittent-Continuous (Leduc) current, &c. Clearest arrangement of Switches, Terminals, M-Ammeter, Reverser, Watteville Key, &c. Motor and Base absolutely Dustproof and Fool-proof; All parts protected from injury. Works from any Electric LampHolder or Accumulators. General Catalogue of 350 pages, fully illustrated and with interesting reading matter, &c. The SANITAS ELECTRICAL CO., Ltd., 61 New Cavendish Street, London, W. THURSDAY, SEPTEMBER 30, 1909. APPRECIATIONS OF CARL VON LINNÉ. THIS der Dr. C. A. M. Lindman is responsible for the next memoir, “C. v. L. als botanischer Forscher und Schriftsteller," and is the longest of the series. Beginning with Linné's early training and first catalogues Carl von Linné's Bedeutung als Naturforscher und of local plants, it deals with that wonderful series of Arzt. which the Schilderungen herausgegeben books von were printed in Amsterdam, Königl. Schwedischen Akademie der Wissenschaften "Systema Naturæ," "Genera plantarum," "Flora anlässlich der zoo-jährigen Wiederkehr des Geburts- lapponica," "Hortus Cliffortianus," &c., especially tages Linné's. Pp. iv+168; 48; 43; 188; 86, 2 pl.; drawing attention to such parts of Linné's botanical 42. (Jena: G. Fischer, 1909.) Price 20 marks. teaching which are apt to be overlooked, such as his attempts at a natural system, and observations in morphology and physiology of plants; of these, many are to be found in his dissertations and travels, rarely looked at now. Indeed, Linné's books are chiefly referred to at the present day from the systematic point The fact that his busy mind had occupied of view. itself on problems which even now are unsolved is lost sight of, because his observations must be sought for in their original Latin or Swedish dress. The latter portion especially of Dr. Lindman's work should be carefully read, and will heighten our wonder at the enormous amount of work accomplished by the occupant of the Chair of Botany at Upsala. HIS volume is a German version of that issued in May, 1907, by the Royal Swedish Academy of Science, and consists of six appreciations of the great Swedish naturalist. The first of these, by Emeritus Prof. Otto E. A. Hjelt, was written at the request of the Academy, and is a revised edition of a former work prepared for the celebration of the quatercentenary of Upsala University in 1877, embodying various improvements through recent investigation into Linnean matters, due to the devotion of the late Dr. E. Ährling and Prof. T. M. Fries. In common with the other essays, this is separately paged, and may be procured apart from its accompanying discourses. Linné's remarkable services to botany and zoology have thrown somewhat into the shade his acquirements as a practising physician and professor of medicine. This essay will do much to draw attention to this side of Linné's activities. It must not be forgotten that he was rescued from a suggested apprenticeship to a tailor or shoemaker, by the sagacity of his early teacher, Rothman, who assured Nils Linnæus that his son showed great aptitude for medicine. It was as for this that Linné entered the University of Lund, and afterwards migrated to Upsala for further improvement; he took his degree of M.D., to earn a livelihood, and he practised in Stockholm after his return to Sweden. His first chair at Upsala was of medicine, and though soon afterwards he exchanged it for that of botany, he continued to keep in touch with it during his career, and left manuscripts showing his unabated interest, in spite of his exertions in other directions. A list of his medical writings at the end of this essay contains eighty-six titles. This is followed by "Carl von Linné und die Lehre von der Wirbelthieren," of Prof. Einar Lönnberg, in which a résumé is given of Linné's predecessors in zoology, from Conrad Gesner, Rondelet, Aldrovandi, and others, to Ray and Willoughby, and contrasting the order brought in by methodical arrangement under Classes, Orders, and Genera. The third essay, "Carl von Linné als Entomolog," is by Dr. Chr. Aurivillius, and is here separately given; in the original Swedish edition, Linné was considered as a zoologist, in a joint memoir with the previous author, but in this issue the part of each writer is set out separately.. Following the same line of thought as in the foregoing essay, Dr. Aurivillius points out that the collections formerly belonging to Queen Lovisa Ulrika at Drottinngholm and of King Adolf Fredrik at Ulriksdal, which had been arranged and catalogued by Linné, have been in the keeping of the University of Upsala since 1803. Linné regarded as a geologist forms the next part of this volume, and is due to Prof. Nathorst; it is illustrated with two plates, and ten figures in the text. Both as petrologist and palæontologist the merits of Linné are set out, and his keen insight into geologiLinné had but little opcal causes are dwelt upon. portunity as a field geologist; his travels were practically bounded by his official journeys to Gotland, Westgotland, and Skåne, and yet his observations merit careful reading in the light of modern science. A similar appreciation is given by Prof. Sjögren in the last section, "Carl von Linné als Mineralog." The Linnean collection of minerals was sold by Dr. J. E. Smith in 1796, when about to remove from Chelsea to Norwich, and its present condition and place are unknown. But it is enough to gather from the various statements in the writings of Linné to put before us the views of the great naturalist. in honour of whom these essays were composed. The chief difference noticed between the original and the present edition is the omission of the reprint which formed an of Linné's "Clavis medicinæ," appendix of ninety pages to Prof. Hjelt's memoir. B. D. J. templated by the author, but his decease prevented its production; and the present work is to be regarded as a substitute. It is a translation of Heil and Esch's 66 Handbuch der Gummiwarenfabrikation," adapted for English usage in respect of the machinery generally employed in this country. Non-technical readers may be reminded that crude rubber as imported contains a number of impuritieswater, woody tissue, sand, and other mineral matter. Moreover, it is unvulcanised, and to fit it for diverse uses various "filling" substances must be incorporated with it. The process of manufacture consists, therefore, in the purification of the raw material; the mixing of this with ingredients which will impart the required colour, durability, or other special property to the article; the fashioning of this plastic mixture into tyre, tube, or whatever finished article is desired; and lastly, the vulcanisation of the object with sulphur, or chloride of sulphur, whereby the rubber becomes non-adhesive, harder, and more durable. The authors give the plan and arrangement of a factory for the carrying out of these operations in what they consider to be the most advantageous manner. They direct special attention to the necessity for excluding dust in the making-up of rubber goods, since leaky seams are liable to develop in goods if particles of dust are allowed to settle on the edges of the article during the joining process. Another point to which they direct attention is the necessity, after the rubber has been washed free from admixed impurities, of drying it in a rational way. Far too little regard is had to this important detail. The large surface-area exposed favours atmospheric oxidation of the moist, warm rubber, and the time of exposure should therefore be as short as practicable. On the -other hand, if the material is imperfectly dried, goods made from it are liable to rapid deterioration. To -dry it thoroughly, quickly, and safely is the desideratum; and the authors describe modern drying-rooms and centrifugal plant adapted to this purpose. While not recommending any one method as the best in all circumstances, they discuss the general principles involved, and plead for an intelligent application of them. ent factories; and the empirical methods evolved are guarded as trade secrets. In fact, so perfectly has long experience developed the rule-of-thumb indications that the authors think scientific investigation can hardly result in any noteworthy revolution in the methods of manufacture. It may be so; but this is not quite the spirit in which progress is made. A few years ago indigo-planters would have said much the same thing. Many illustrations accompany the text, which is generally lucid, though occasionally with a leaning to Teutonic stolidity. Except in this respect, the translator has eliminated any lingual indication of the origin of the book, which can be recommended as a very practical and useful work. C. S. VECTOR ANALYSIS. Vector Analysis: an Introduction to Vector-methods and their Various Applications to Physics and Mathematics. By Dr. J. G. Coffin. Pp. xix+ 248. (New York: John Wiley and Sons; London: Chapman and Hall, Ltd., 1909.) Price 10s. 6d. net. THIS 66 Introduction to Vector-methods and their Various Applications to Physics and Mathematics" is an exposition of the late Willard Gibbs' vector analysis. The author in his preface warns us that "no attempt at mathematical rigor is made ❞— which perhaps explains the opening sentence of chapter i.: "A vector is any quantity having direction as well as magnitude." What of finite rotations? Are they not to be considered quantities having direction and magnitude? In an appendix the author compares notations, not always quite accurately. He believes Willard Gibbs' notation to be the simplest and most symmetrical of any of the existing kinds. Burali-Forti and Marcolongo, who believe they have devised the perfect notation, object to Willard Gibbs's "dot" in the scalar product, using a "cross" instead. As regards the question of symmetry, the truth is that the vector product is not symmetrical, for in Gibbs's notation axb-bxa. As a matter of fact each vector analyst can always find sufficiently self-pleasing arguments in favour of his pet notation. Notation apart, the book is well put together, and lays stress on many important applications in dynamics, elasticity, hydrodynamics, electricity, and magnetism. The differential operator v, in its Gibbsian phase, is developed in considerable detail. But will non-Hamiltonian vector analysts never realise how much they lose by working with what is not, after all, the real Hamiltonian operator? By discarding the associative law in vector products they lose the flexibility of the real v. Pages of definitions would be saved by a simple return to Hamilton and Tait; and not only so, but the mind of the student would be freed from the task of committing to memory the laws of the equivalent operators as used by Gibbs, Heaviside, Gans, Jahnke, Bücherer, Föppl, Burali-Forti and Marcolongo, &c. In the exercises at the end of chapter v. we notice two mistakes. In exercise (4) we are told that v.(a × r) = 2a, where a is the length of the vector a. In quaternions this is S▾ Vap. But Vap 2a, a |