DENT'S CLOCKS, BUTLER'S "SWINGCAM" STAND. A SPECIALITY IN TRIPODS. THE FOR SCIENTIFIC USE. E. DENT & CO., Ltd., By Special Appointment to H.M. the King. GREENWICH, AND THE Only Addresses- (Flexural Method). With Four Bars, £2:0:0. Scale 1. TESTIMONIAL from Mr. R. KEARTON, F.Z.S. Caterham Valley, Surrey, August 4th, 1960 Dear Mr. Butler, I have much pleasure in stating that I have put your new "Swingcam I remain, Yours ever faithfully, R KEARTON MARK TRADE DENT WM. BUTLER, 20 Crosby Road, Southport. (Late MOTTER8HEAD & CO.). FREDK. JACKSON & Co. 14 CROSS STREET, MANCHESTER. LABORATORY FURNISHERS, Goods Entrance : 10 Half-Moon Street. SCIENTIFIC WORTHIES. A List of this Series of Steel and the Publishers. Importers, Manufacturers, and Dealers in Of every Description. PLAIN AND STOPPEREO BOTTLES. Chemicals, free on application. Telephone Number—7238. POST OFFICE BRIDGE SETS AND INDUCTION COILS A SPECIALITY. ELECTROMETER, NEW PATTERN. 56 W.C. MACMILLAN & CO'S LIST, THE GEOLOGY OF SOUTH AFRICA. By F. H. HATCH, Ph.D., M.Inst.C.E., President of the Geological Society of South Africa ; and G. S. CORSTORPHINÉ, B.Sc., Ph.D., Consulting Geologist to the Consolidated Coalfields of South Africa 8vo. 215. net. MINING WORLD._"The authors are to be congratulated on their success. . . . It deserves, and will no doubt have, a wide circulation." NEW AND REVISED EDITION, NOW READY. A TREATISE ON CHEMISTRY. 2IS. net. By SIR H. E. ROSCOE, F.R.S., and C. SCHORLEMMER, F.R.S. Vol. I. — The Non-Metallic Elements. New Edition, completely revised by Sir H. E. Roscoe, assisted by Dr. H. G. COLMAN and Dr. A. HARDEN. With 217 Illustrations. 8vo. ATHENA UM.-" It is almost superfluous to say that the work maintains its original high standard, and is p:e-eminent among works of its class in all languages.” WATKINS & DONCASTER, PHENIX FIRE OFFICE. ESTABLISHED 1782. Prompt Payment of Olaims. Naturalists and Manufacturers of BRANCHES OF NATURAL HISTORY. Classes, &c. Workmen true to Nature. (Five Doors from Charing Cross.) I New Catalogue (102 pp.) just issued, post free. GLASS BLOWING. All kinds of Scientific and Experimental Any form of Glass Apparatus repaired. Also Hand Painted from 1/3 to 5/- each. PHOTOMICROGRAPHS. 600, 14/6; 1200, 25/6. See List. MICROSCOPICAL SLIDES, Botanical, Zoological, 1 &c., from 6s. per dozen. FLATTERS & GARNETT, Ltd., 48, DEANSGATE, And at Church Road, LONGSIGHT, MANCHESTER. H. HELM, 66 HATTON GARDEN, LONDON, E.C. ROCKS, MINERALS, FOSSILS. For Collectors, Students, Technical Schools, Colleges, &c. COLLECTIONS IN POLISHED DEAL BOXES. 25 Specimens, 5/6 ; 50 do., 10/6 ; 100 do., 21/- ; 200 do., 42/Actual Maker of all kinds of X-Ray and Vacuum Tubes, 20 Coal Measure Rocks and Fossils, 12/6; do., larger, 15%-. Mercury Pumps, High Frequency Electrodes, &c. Adapted for the Board of Education Examinations in Geology, Physiography, and Mineralogy. selection. Specimens sont on approval. LIVING SPECIMENS FOR Cabinets, Geologists' Hammers, Chisels, Card Trays, Qlass-capped Boxes, Models of Crystals, &c., &c. NEW CATALOGUE POST FREE. Volvox, Spirogyra, Desmids, Diatoms, Amceba, Arcella, Actinosphærium, THOMAS D. RUSSELL, 78 Newgate St., London, E.C. Vorticella, Stentor, Hydra, Floscularia, Stephanoceros, Melicerta, and many other specimens of Pond Life. Price is. per Tube, Post Free. Helis pomatia, Astacus, Amphioxus, Rana, Anodon, &c., for Dissection purposes MICROSCOPICAL PETROGRAPHY, THOMAS BOLTON, Gentlemen interested in the above study are invited to send to 25 BALSALL HEATH ROAD, BIRMINGHAM. JAMES R. GREGORY & CO., MARINE BIOLOGICAL ASSOCIATION ı Kelso Place, Kensington Court, London, W., OF THE UNITED KINGDOM. for a Prospectus of THE TWENTIETH CENTURY ATLAS OF THE LABORATORY, PLYMOUTH. MICROSCOPICAL PETROGRAPHY, The following animals can always be supplied, either living now being issued in Twelve Monthly Parts, each Part containing Four Fine or preserved by the best methods : Half-Tone Plates, and also Four actual Rock Sections. Sycon ; Clava, Obelia, Sertularia ; Actinia, Tealia, Caryophyllia, Alcy. oniun; Hormiphera (preserved); Leptoplana; Lineu«, `Ampbiporus, Subscription in advance, either Monthly, 7/-; Quarterly, 21/.; Nereis, Aphrodite, Arenicola, Lanice, Terebella; Lepas, Balanus, or for the whole Series of 12 Monthly Parts & 48 Sections, £4 4s. Gammarus, Ligia Mysis, Nebalia, Carcinus ; Patella, Buccinum, Eledone, Pectens Bugula, Crisia, Pedicellina, Holothuria, Asterias, Echinus, Ascidia, Salpa (preserved), Scyllium, Raia, &c., &c. PHOTOMICROGRAPHY for Publishers, For prices and more detailed lists apply to Lecturers, Manufacturers, and general scientific research. Good work, Biological Laboratory, Plymouth. THE DIRECTOR. moderate charges.-Saxby, 91 Penny Lane, Sefton Park, Liverpool. 8 I 10 6 2 o . . NOTICE.-Advertisements and business letters for NATURE should be addressed to the Publishers; Editorial CHARGES FOR ADVERTISEMENTS. £ s. d. Yearly Yearly 6 Quarter Page, or Half Per Line after 9 a Column I 15 0 15 6 One Sixteenth Page,or Eighth Col. 10 Quarterly Quarterly o 7 6 Half a Page, or a Column 3 S 018 6 | Whcle Page. OFFICE: ST. MARTIN'S STREET, LONDON, W.C. o From the New Issue of W. WATSON & SONS' No. 3 CATALOGUE, just published. Post Free on application. Tsetse Flies (G. palpalis), whole insect 6 Perfume Glands on Leaf of Lavender ... Dissections of all parts may be had mounted separately. Also in Bugula plumosa (Bird's Head coralline). Specially fine mounts 2 set of 12 £10 Karyokinesis in root of Water Lily ... "Send for Special Descriptive List.*** Leg of Flea, showing muscular structure Blood-sucking Maggot (from the Congo) ... . Set of 16 Slides illustrating the development of an Ascidian Fly hatched from above, Auchmeromyii luteola 76 (Aspersa). In case ... ... ... Section of Brazilian Quartz, showing cavities containing fluid. Trypanosorna Brucei (Tsetse Fly disease) Very interesting Set of 5 Slides of the Garden Spider, showing different stages of Eggs of Emperor Moth, fertile and sterile, on 1 slide growth. la Case ... ... ... ... ... ** SEND FOR THE ABOVE NEWLY PUBLISHED CATALOGUE OF MICRO. OBJECTS. WATSON'S CATALOGUE OF MICROSCOPES (158 pages) is of special interest to all Microscopists, post free. W. WATSON & SONS, 313 High Holborn, London, W.C. Branches-16 FORREST ROAD, EDINBURGH, and 2 EASY ROW, BIRMINGHAM. CROSSLEY'S GAS ENGINES RECENTLY GREAT REDUCTION REMODELLED. Represents K and L CAS CONSUMED. types, giving 3.5 H.P. Up to the end of 1904, and 5 H.P over 51,000 gas and respectively. oil engines had been ANCHESTES delivered, representImmediate Delivery ing about threefor Stock Sizes quarters of a million of Engines. actual horse-power. CROSSLEY BROS., LTD., OPENSHAW, MANCHESTER DALLMEYER'S IMPROVED Will not get out of Adjustment. Easy to Clean. Powers 4, 6, 8, 10, 12. e Illustrated Pamphlet Post Free. 25 NEWMAN ST., LONDON, W. Makers of the Celebrated Dallmeyer Lenses. junteu by RICHARD CLAY AND SONS, LIMITED, at 7 & 8 Bread Street Hill, Queen Victoria Street, in the City of London, and published by MACMILLAS AND Co., LIMITED, at St. Martin's Street, London, W.C., and The MACMILLAN COMPANY, 66 Fifth Avenue, New York. -THURSDAY, Septemleri EN A WEEKLY ILLUSTRATED JOURNAL OF SCIENCE “ To the solid ground Oj Vature inusis the mind which builds for aye.” IORDSWORTII. No. 1873, VOL. 72] THURSDAY, SEPTEMBER 21, 1905. [PRICE 15 CENTS Registered as a Newspaper at the General Post Office.) All Rights are Reserved. Apparatus for the determination of the relative conductivity of thin layers of materials. NEGRETTI & ZAMBRA'S LONG RANGE BAROMETERS THE DIAGONAL BAROMETER.-In this instrument the tube is much longer than usual, and at the point on the vertical column where in ordinary Mercurial Barometers the 23 inches would be marked, the tube is bent at an angle and the remaining 3 inches of the scale-viz. : 29, 30. and 31are extended over a tube 36 inches long. The mercury now moving diagonally instead of vertically, travels over 12 inches of the tube to every inch on the vertical scale. The slightest variation, even o1" to which the scale is divided, is at once noticeable ant can be easily read without the aid of a vernier or magnifier. LEES' & CHORLTON'S METHOD. Catalogue of Part U., free on application. JOHN J. GRIFFIN & SONS, Ltd., 20-26 SARDINIA ST., LINCOLN'S INN FIELDS, Further Particulars and prices of this and other long ringe Barometers sont on application to the Manufacturers. NEGRETTI & ZAMBRA, 38 HOLBORN VIADUCT. BRANCHES : 45 CORNHILL, AND 122 REGENT STREET, |