BIRKBECK COLLEGE. BREAMS BUILDINGS, CHANCERY LANE, F.C. FACULTY OF SCIENCE. Chemistry Physics ... Mathematics Botany Zoology... fJ. E. MACKENZIE, Ph.D., D.Sc 1 H. WREN, Ph.D., B A., B.Sc. ALBERT GRIFFITHS, D.Sc. D. OWEN, B.A., B.Sc. B. W. CLACK, B.Sc. E. H. SMART, M.A. W. G. BIRT, B.A, B.Sc. A. B. RENDLE, M.A., D.Sc. F. E. FRITSCH, Ph.D., B.Sc. H. W. UNTHANK, B.A., B.Sc Geology & Mineralogy GEO. F. HARRIS, F.G.S. Assaying, Metallurgy & Mining. GEO. PATCHIN, A. R.S.V. RESEARCH in Chemistry and Physics in well-equipped laboratories. French, German, Spanish, Russian, Dutch, & Italian Classes. EVENING CLASSES also in Biology, Physiology, Practical Geometry, Building and Machine Construction, Steam, Theoretical and Applied Mechanics, Land and Quantity Surveying, and Estimating. Calendar 6d. (post free 8d.), on application to the SECRETARY TYPE-WRITING UNDERTAKEN BY HIGHLY EDUCATED WOMEN ACCUSTOMED TO SCIENTIFIC MSS. (Classical Tripos, Intermediate Arts, Cambridge Higher Local, thorough acquaintance with Modern Languages). Research, Revision, Translation. Scale of charges on application. The Cambridge Type-writing Agency, to Duke Street, Aldephi, W.C. ALFRED E. DEAN, THE LARGEST MAKER IN ENGLAND of Apparatus in all Departments of ELECTRO-THERAPEUTICS including Radiography, High Frequency, Hydro-Electric and FOR SALE. 30 moving coil ammeters and voltmeters. 6 moving coil reflecting and pointer galvanometers. 8 hot wire ammeters and voltmeters. 50 electromagnetic ammeters and voltmeters. 60 dynamos and motors, direct and alternating current. 40 ironclad regulating rheostats. 20 transformers and choking coils. 10 induction coils, 10-inch spark. 3 mercury jet breaks. Standard condensers, Wheatstone bridges, static machines, switches, cables, &c., by various makers, at low prices. G. BOWRON, 57 EDGWARE RD., LONDON, W. page 232. Descriptive Inexpensive. THE NEW PATENT PRICE 21/ PIESMIC BAROMETER. To be obtained of all Opticians, or the SOLE MAKERS, F. DARTON & CO., CLERKENWELL OPTICAL WORKS, 142 ST. JOHN STREET, LONDON, E.C. ORTHOCHROMATIC PHOTOGRAPHY. A SANGER-SHEPHERD Light Filter gives the Maximum of Orthochromatic effect with the Minimum of Exposure. To obtain Pictures true to nature with correct values of Light and Shade, Shadow Details and Cloud Effects, use a Sanger-Shepherd Light Filter. All sizes stocked-Circular and Square. Fittings and Cases SETS OF LIGHT FILTERS in Special Case, morocco-covered, velvet-lined, for pocket. X 5 times. For Cloud Effects and Snapshots X 10 times and Gilvus. For Landscapes and Portraiture Absolutus. For correctly copying all coloured objects from 76 from 10 from 10/ Send for New Booklets, post free to readers of "Nature," or call and see results obtained by Amateurs. SANGER-SHEPHERD & CO. FACTORY AND OFFICE: 5, 6, 7 GRAY'S INN PASSAGE, RED LION STREET, HOLBORN, W.C. Apparatus for estimation of sulphur in spent oxide. FREDK. JACKSON & Co. (Late MOTTERSHEAD & CO.), 14 CROSS STREET, MANCHESTER Goods Entrance: 10 Half-Moon Street. LABORATORY FURNISHERS, Importers, Manufacturers, and Dealers in Of every Description. Fine Chemicals, Volumetric Solutions, AND EVERY LABORATORY REQUIREMENT. FOR SALE, at Reduced Prices. MICROSCOPIC SLIDES (dispersal of Mr. Hornell's collection), see Micro. Editor's note, June No. of Knowledge, Sections of Flower Buds, &c., also Marine, suitable for Students and Exhibition, new, prices from 3d. each. MICROSCOPE, Baker's D.P.H. and fittings, £7 16s.; Beck's London and fittings, £6 6s.; many others, Pillisher, Ross, &c. Several Objectives. Bull's-Eye Condensers. Abbe Condensers. Eyepieces by Leitz, &c. Goerz PRISMATIC BINOCULARS. Photographic Lenses. SURGEON'S OPERATION Outfit, very fine, new, for sale, cheap. Collection of Shells. Many other useful articles. Send for lists. Mr. HERBERT CLARKE, 104 LEADENHALL STREET, LONDON. THE PRICE 15/ "DEMON" GEISSLER TUBE, WARNING. Observe that the Regulator of Burner, Body of Furnace, and Hood are all distinctly stamped in the metal "BREWSTER, SMITH & Co., LONDON." Beware of imitations that do not contain the essential feature of this burner's success. MARBLE REDUCED TO QUICKLIME IN 10 MINUTES with our NEW BLAST BUNSEN BURNER AND MIDGET FURNACE. We make these in two sizes at present," and ", and the prices are-Burners only, 1/6 and 2:6; complete with Furnace, 4/6 and 6/ The consumption of gas is the same as with an ordinary Bunsen, but the heat derived is three times as great, and a number of interesting experiments can be performed with them, which have only been possible before with very expensive furnaces. We are the SOLE MAKERS. NATURE says:-"The combination of furnace and burner is very convenient. These little furnaces are not only useful for reducing calcium carbonate to lime, but also work very well in fusion experiments." BREWSTER, SMITH & CO., LABORATORIES FITTED & FURNISHED THROUGHOUT. SECOND-HAND MICROSCOPES. (Monocular and Binocular.) Dublin: EASON & SON, LTD, 40 Lower Sackville Street (to which Address Subscriptions should be sent). London: SIMPKIN, MARSHALL, HAMILTON, KENT, & CO., Ltd PEAK (BY APPOINTMENT TO THE ROYAL INSTITUTION OF GREAT BRITAIN.) READING MICROSCOPES, RESISTANCE COILS, &c. 56 CHARING CROSS ROAD, LONDON, W.C. SPECIAL TERMS TO COLLEGES, SCHOOLS, INSTITUTES, &c. RADIUM ON HIRE. TERMS ON APPLICATION. W. MARTINDALE, MANUFACTURING CHEMIST, 10 NEW CAVENDISH ST., LONDON, W. Telephone: 1797, PADDINGTON. Telegrams: MARTINDALE, CHEMIST, LONDON. Pitchblende, from 2/- to 30/- per piece; in Powder, 2/6 per oz. Rad. Residue, 2/- per tube. Polonium, 21/- per gram; 11/-.gram Flexible Sandstone, 5/- to 50/-. (See NATURE, June 23, 1904, Monazit, 3/- per oz. Monazit Sand, 1/- per oz. Bar. Plat. Cyan., for Screens, 3/- gramme, 60/- oz. Crystals, 4/- Radio-active screens, 6d. per square inch. Willemite screens, 6d. per square inch. Electroscopes (special), 21/Spinthariscopes (special), 21/-, 10/6 and 7/6. Selection of Minerals in boxes, 2/6, 5/6, 10/6 and 21/-. New Zealand Vegetable Caterpillar, with a stem showing fructification growing out of its head, 10/6 to 21/- each. See NATURE, May 12, 1904. CALCIUM METAL, 1/6 per oz. All Post Free within U.K. Goods may be returned if not approved of, when money will be refunded. ARMBRECHT, NELSON & CO., W. G. PYE & CO., IMPORTANT.-Note also how close the terminals for the unknown value are together, and that a double 5 J. B. LIPPINCOTT COMPANY, HENRIETTA STREET, COVENT GARDEN, LONDON. MAY BE OBTAINED THROUGH ANY OPTICIAN. If any difficulty be found in securing any of our Instruments through your Dealer kindly communicate with the Manufacturers, PASTORELLI & RAPKIN, (Established 1750), Contractors to H. M. Government, LTD. 46, HATTON GARDEN, LONDON, E.C. Telephone No. 1981, Holborn. Telegrams-"Rapkin, London." SUSPENDED COIL With interchangeable coils, each contained in a dust-tight case. FIGURE OF MERIT. 10 MILLIMETRES per MICROVOLT at a scale distance of 1 metre with 25 ohm suspended coil. Price, without tangent-head £6 O with 7 (Including 25 ohm' coil unless otherwise ordered.) Spare coils (5 ohms or 200 ohms) mounted as shown to right of figure each 3 THE CAMBRIDGE SCIENTIFIC INSTRUMENT COMPANY, LTD. |
