KING'S COLLEGE, LONDON. (UNIVERSITY OF LONDON.) The Council invite applications for the post of JUNIOR DEMON. STRATOR in ENGINEERING. Applications should be sent in by Friday, September 15, 1905. WALTER SMITH, Secretary. KING'S COLLEGE. (UNIVERSITY OF LONDON.) DEMONSTRATOR in ZOOLOGY wanted for October, 1905. Salary, L150. For further particulars apply to the SECRETARY, King's College, Strand, W.C. MERCHANT VENTURERS' TECHNICAL COLLEGE, BRISTOL. ASSISTANT LECTURER and DEMONSTRATOR in ENGINEERING required. Salary, £170, which may rise to £220. Particulars obtainable from the REGISTRAR by sending a stamped addressed foolscap envelope. Applications should be sent in not later than September 18, 1905. To SCIENCE and MATHL. MASTERS. REQUIRED immediately for Secondary School near London, Master to take Elementary Science and Geograp' y. £150 to commence. Also Mathl. Master for School in W. London. Maths., including New Geometry. £170. Many other vacancies.-Addres GRIFFITHS, SMITH, POWELL & SMITH, Tutorial Agents (Estd. 1833), 34 Bedford Street, Strand, London. Wanted for St. Augustine's Seminary, Dun garvan, Co. Waterford, a Teacher of Chemistry and Physics. Must be a B.Sc. with honours in Chemistry. Salary £140. Non-resident. To take up his duties before October 15. Newbold Rectory, Stratford-on-Avon.-Home School for a limited number of pupils. Science a speciality. Laboratory and Observatory. Fees moderate.-Apply G. A. S. ATKINSON, B.Sc. (Lond.). DUBLIN UNIVERSITY. SENIOR DEMONSTRATOR of PHYSIOLOGY wantel. mencing salary, £175. Applications to REGISTRAR, Medical School. Com 0.50 0'30 NATURE says:-"In the excellence of their 1/12-in. homogeneous oil immersion, they have pro luced an English-made lens of first-rate capacity which is a marvel of cheapness." LISTS POST FREE ON APPLICATION. UNIVERSITY OPTICAL WORKS. 81 Tottenham Court Road, London. GLEW'S SCINTILLOSCOPE (PATENT). Shows a magnificent display of scintillations, showers of sparks, direct from the mineral Pitchblende, Radium, Polonium, Uranium, Thorium, or any radio-active substance, even a Welsbach mantle contains sufficient Thorium to excite the very sensi tive screen of the Scintilloscope, which is far more sensitive than the Spinthariscope. The Scintil loscope rivals the most delicate Électroscope as a detector of Alpha rays. The eye sees an inexhaustible shower of stars of PITCH BLENDE white light, giving a very realistic idea of the ceaseless activity of these marvellous substances which are producing the terrific bombardment causing this beautiful display. See NATURE, September 29, page 535.. Glew's Scintilloscope Superior Lens, with Extra-sensitive Pitchblende and Polonium Screens, giving brilliant effects, Complete, 75. 6, Post free, U.K. Foreign Postage extra, weight 2 ounces. Pieces of Pitchblende mineral, ground flat and polished, with Sensitive Screen attached, for use in Scintilloscope or with any strong pocket magnifier, from 75. 6d. each, according to size. Radio-active supplies of every description, on Sale or Hire. Radium Bromide 1,800,000 units on hire for lectures. F. HARRISON GLEW, Radiographer (Silver Medallist, Paris, 1900), 156 Clapham Road, London, S. W. RARE CHEMICALS For Laboratory, Scientific, and all other purposes. RADIUM SALTS & RADIO-ACTIVE PREPARATIONS. CALCIUM METAL, 1/6 oz.; 20-lb. Price List on Application. HARRINGTON BROS., Chemical Manufacturers and Dealers, 4 OLIVER'S YARD, CITY ROAD, LONDON, E.C. IMPORTANT REDUCTION IN PRICE. SPINTHARISCOPE. AS DEVISED BY SIR WILLIAM CROOKES. Showing the Scintillations of Radium. Price with powerful Lens, and contained in neat Leather case, 15/- Post free anywhere. The scintillations seen in this instrument are from Pure Radium Bromide of the highest known activity, and are brighter and more plentiful than those produced from Pitch blende or other bodies of low Radio Activity. See letter from PROF. GOTCH on "The Spinthariscope and Retinal Excitability" (NATURE, June 22, 1905, page 174), setting forth a valuable scientific application of the instrument. A. C. COSSOR, 54 FARRINGDON ROAD, LONDON, E.C. Telephone. 10547 Central. Gold Medal St. Louis Exhibition, 1904. SCIENTIFIC WORTHIES. A List of this Series of Steel and Photogravure Portraits of Men of Science will be sent post free to any reader of "Nature" on application to the Publishers. ST. MARTIN'S STREET, LONDON, W.C. HEELE'S FAMOUS DIRECT VISION SPECTROSCOPE With 10 prisms. Dispersion: 25°. The Telescope has Micrometer-screw with divided drum for Wave- Do. Do. with 5 prisms, dispersion 12°. ADVANTAGES: Always adjusted and ready for use. DELIVERY FROM S TO CK. AS SUPPLIED TO THE Royal College of Science, South Kensington, London, S.W. Woolwich Polytechnic, Woolwich, London, S.E. PETER HEELE, 115 High Holborn, London, W.C. Maker of Physical, Chemical, and other Instruments, and every kind of Spectroscope and Polarimeter. GRAND PRIX, PARIS, 1900; ST. LOUIS, 1904. Telegrams: "ARCTITUDE, LONDON." DEPREZ SIGNAL, SINGLE A style for writing on smoked paper is attached to the arma ture of an electro- SCIENTIFIC INSTRUMENT COMPANY magnet, and when the magnet is excited the style suffers a small displacement of adjustable amount. The apparatus is very small with extremely light moving parts. It is readily clipped to the stem (10 mm. diameter or under) of a simple stand, and fine adjustment is provided for bringing the style up to the paper. In the double form (as illustrated) two styles with independent electro-magnets are mounted side by side. If desired, one may be connected with a pendulum or tuningfork interrupter to mark time while the other registers the events to be investigated. SINGLE DEPREZ SIGNAL, complete in box, £2 10s. DOUBLE DEPREZ SIGNAL, complete in box, £3 10s. THE CAMBRIDGE SCIENTIFIC INSTRUMENT COMPANY, LTD., CAMBRIDGE, ENGLAND, CARL ZEISS, JENA. THE JUBILEE CATALOGUE ISSUED TO MARK THE FIFTY YEARS' EXISTENCE OF THE FIRM OF E. LEYBOLD'S NACHFOLGER, COLOGNE, Contains on its more than 900 pages a complete survey of the apparatus used for instruction in Physics, as well as numerous practical instructions and about 3000 illustrations. NATURE says:-"The firm of Leybold Nachfolger in Cologne has recently issued a very complete and interesting catalogue of physical apparatus and fittings sold by them. The book starts with a history of the instruments made in Cologne during the last century. In its second section we find an account of the construction and fittings of various chemical and physical institutions. After this follows the catalogue proper, filling some 800 large pages, profusely illustrated and admirably arranged. The book will be most useful to the teacher." (No. 1846, Vol. 71.) A. KERSHAW, Dorrington St., Leeds. THE CATALOGUE WILL BE FORWARDED TO SCHOOLS THURSDAY, SEPTEMBER 7, 1905. MARINE ENGINEERING. Marine Engines and Boilers, their Design and Construction. Based on the work by Dr. G. Bauer. Translated from the second German edition by E. M. and S. Bryan Donkin. Edited by Leslie S. Robertson. Pp. xxviii+744. (London: Crosby Lockwood and Son.) Price 25s. net. THIS HIS considerable work fills a gap in English engineering literature. For while the related subject of naval architecture has been treated by writers of authority, there is no very good modern book on marine engineering. Dr. Bauer states that it is intended to be a condensed treatise, embodying the theoretical and practical rules used in designing marine engines and boilers. But though thus limited in scope, it treats only of the most modern types and excludes even modern engines and boilers of special types. As might be expected from the engineer-in chief of the Vulcan Works at Stettin, the machinery of warships and of some of the great German Atlantic liners are very fully illustrated. There is not a great deal of theoretical investigation, but what there is bears very definitely on design, and is sound so far as it goes. Perhaps the most valuable part of the book is the great amount of tabulated information about the proportions of the machinery in good examples of modern practice. There is also a very large collection of those empirical or semi-empirical rules, based on extensive practical experience, on which engineers necessarily so much rely. There is reason to be grateful that an engineer so distinguished as Dr. Bauer, with the care of a great factory on his shoulders, should have found time to produce such a systematic treatise, and that he has been able to obtain the aid of some of his principal technical assistants in dealing with parts of the subject. The book has been excellently and competently translated, and the translators have undertaken the necessary, but very laborious, task of converting the numerical statements of formulæ from the metric to English measures. However bad our English system of measures may be, English engineers can only think and work in English measures, and the translation would have lost very much of its usefulness if the conversion had not been made. Mr. Leslie S. Robertson, who has edited the volume, has had practical experience in this branch of engineering, and has already published valuable works relating to it. His name is a guarantee that the adaptation of the work for English readers has been, from the technical point of view, thoroughly well done. The general arrangement of the book is convenient. Part ., which occupies four-tenths of the volume, deals with the main engines. First, indicator diagrams are discussed, and the application of theoretical diagrams in settling cylinder proportions. The well known method of constructing theoretical diagrams from a diagram of the volumes occupied by the steam is given, and an example worked out. The remark is made that "the diagrams so obtained show the characteristics of actual diagrams, but their mean pressures are naturally much higher than they would be in actual practice." That is not our experience. If the data are rightly used, there is a fairly close approximation between the theoretical and actual mean pressures. It is a case in which the precise law of expansion assumed does not very much affect the result. There is one other small point in this chapter. The ratio of an actual to a theoretical diagram is called an "efficiency" (p. 17). This leads to the awkward statement on p. 35 that "the efficiency of triple expansion engines is less than that of single cylinder engines." If the more usual term diagram factor" had been used instead of efficiency the statement would be less misleading. Next there is a very short section dealing with some thermal circumstances affecting the utilisation of steam. This is too brief to be satisfactory, even from the point of view of engine design. For instance, the loss due to cylinder condensation is explained by saying that "heat is withdrawn from the steam at high pressure and restored to it at a lower pressure (p. 37). The essential point that the heat is chiefly restored during exhaust is not mentioned. So the economy of multiple expansion engines is traced to reduction of temperature range. But the re-evaporation during exhaust from one cylinder increases the work in the next. In other respects also the explanation is deficient. However, the thermodynamics of steam engines is fully given in other treatises. An important section follows, in which the stroke, speed, and turning moment are discussed. The theory of torsional vibrations is given, and practical methods of determining the critical speed at which liability to strong torsional vibrations occurs. In connection with this there is a brief but clear and practical treatment of the problem of balancing. Then the arrangement of main engines is explained, and there is a long section dealing with the proportions of engine details and including a sufficient account of valve diagrams. Part ii. deals with pumps. Part iii. discusses shafting, and in connection with this ship resistance, and the proportioning of propellers. German writers are adepts at tabulating coefficients and data, and the pipes and connections. tables in this section are excellent. Part iv. is on Part v. deals with steam boilers, and is chiefly descriptive of modern types. Here again the tabulated data from actual cases is information of the most useful kind, and the rules of the classification societies, which leave the engineer very little discretion, are fully given. The last section gives some account, rather too much condensed, of instruments used in steam engine and boiler trials. To many readers an account of Fottinger's torsion indicator for measuring the effective horse-power of engines by observing the torsion of the screw shaft will be interesting. Hirn first used a torsion dynamometer of this kind. As a diagram of the torsion angle is obtained, the variation of the power transmitted can be determined. No account is given of the most recent change in marine engineering, namely, the adoption of the steam turbine in place of reciprocating engines. The success of the steam turbine in this field is already so well assured that a revolution in marine engineering is promised. But there are, no doubt, good reasons for the omission. Experience in the use of steam turbines in ships is almost confined to this country, and naturally at present full information as to the results, mechanical and economic, of the use of turbines is only possessed by a few engineers, and is not generally available. In this country we still rightly pride ourselves on retaining the highest position in shipbuilding and marine engineering. But, if we still do more work of this kind than any other nation, and if our best work is as good as any in the world, yet Dr. Bauer's book should remind us that in science, experience and skill, other nations now run us very close. SINCE Special lists are given of the birds of Grimsey and the Westman Islands. Changes in the bird-fauna of the whole group of islands, and the general relationships of the fauna form the subjects of two succeeding chapters, a brief note being appended on domesticated species. This completes the introductory portion of the subject, which occupies ninety-two pages, and the remainder of the text is devoted to the detailed synopsis of the birds. The total number of species, exclusive of the great auk, recorded in the preliminary list as definitely known to occur in Iceland is 120, in addition to which are a few of which the right to a place among the fauna is somewhat uncertain. Perhaps the most striking feature of the descriptive part of the work is the almost painful severity with which new fashions in ornithological nomenclature are followed, such appalling alliterations as Merula merula merula and Gallinago gallinago gallinago occurring with wearisome frequency. Without reiterating his own private opinion on nomenclature of this nature, which is now pretty well known, the reviewer may point out that when the typical form of a species is alone recorded, it is perfectly superfluous to add the terminal trinomial, Merula merula and Gallinago gallinago being in such cases ap Excellent photographs of the eggs, nests, or breeding-haunts of some of the rarer species serve to enliven the text, and ornithologists will be greatly interested in the two pictures of the eggs and callow young of the great skua in their natural surroundings. The work will doubtless long remain the standard authority on Icelandic birds, at all events for German readers. THE BIRDS OF ICELAND. Beitrag zur Kenntnis der Vogelwelt Islands. By B. Hantzsch. Pp. vi + 341; illustrated. (Berlin : Friedländer and Son, 1905.) Price 12 marks. INCE Iceland lies on one of the main migration|parently all that can possibly be required. routes, namely, that which starts from Greenland and Iceland itself, and passes by the Færöes to the British Islands, its bird-fauna is naturally of special interest and importance. This is testified by the appearance within a comparatively short period of two works on the subject, namely, Mr. H. N. Slater's "Manual of the Birds of Iceland," published at Edinburgh in 1901, and the present larger and more pretentious volume. In addition to the general fauna, there is special interest attaching to Iceland as the chief European resort in former days of the gare-fowl, or great auk. The history of this lost bird and the literature relating to it the author reserves for a supplemental volume. Despite all that has been done by travellers and collectors, Mr. Hantzsch is of opinion that our knowledge of the bird-fauna of Iceland is still far from complete, much of the interior of the country being difficult of access and still imperfectly explored by collectors. Accordingly he is fain to admit that the last word on the subject still remains to be said. The volume commences with an historical survey of the growth of our knowledge of Icelandic ornithology, with notices of the chief explorers and workers in this field of research, and a list of the more important memoirs and books treating of the subject. Then comes a detailed account of the author's own journeys in the island for the purpose of collecting specimens and personally observing the birds. This is followed by an interesting description of the main physical features of Iceland and the neighbouring islets, such as Grimsey in the north and the Westman group in the south, this being illustrated with a number of reproductions of photographs of the scenery taken by the author himself. OUR BOOK SHELF. R. L. Neue Fische und Reptilien aus der böhmischen VERTEBRATE fossils are not only rare, but also badly Dr. Bayer's chapter on the Cretaceous fishes was originally published in the Bohemian language in 1902, but is now made more readily accessible in German. He describes evidence of several new genera and species, and concludes that in the of the higher fishes than have hitherto been found Bohemian Chalk there are more varied representatives below the Tertiary formations. In view of the fragmentary nature of most of the fossils, it must be |