Current Accounts. 2% Interest allowed on minimum monthly balances when not drawn below £100. Deposits. 21% Interest allowed on Deposit Accounts. Advances made. Stocks and Shares bought and sold. Apply C. F. RAVENSCROFT, Secretary, Southampton Buildings, High Holborn, W.C. MICROSCOPICAL PETROGRAPHY. Gentlemen interested in the above study are invited to send to JAMES R. GREGORY & CO., 1 Kelso Place, Kensington Court, London, W., for a Prospectus of THE TWENTIETH CENTURY ATLAS OF MICROSCOPICAL PETROGRAPHY, now being issued in Twelve Monthly Parts, each Part containing Four Fine Half Tone Plates, and also Four actual Rock Sections. Subscription in advance, either Monthly, 7/-; Quarterly, 21/-; or for the whole Series of 12 Monthly Parts & 48 Sections, £4 4s. WATKINS & DONCASTER, Naturalists and Manufacturers of CABINETS AND APPARATUS N. B. FOR ENTOMOLOGY, BIRDS' EGGS AND SKINS, AND ALL SPECIAL SHOW-ROOM FOR CABINETS. For Excellence and Superiority of Cabinets and Apparatus, refer. ences are permitted to distinguished patrons, Museums, Colleges, &c. A LARGE STOCK OF INSECTS, BIRDS' EGGS AND SKINS, SPECIALITY.-Objects for Nature Study, Drawing Classes, &c. Birds, Mammals, &c., Preserved and Mounted by First-class Workmen true to Nature. All Books and Publications on Natural History supplied. 36 STRAND, LONDON, W.C. (Five Doors from Charing Cross.) New Catalogue (102 pp.) just issued, post free. ROCKS, MINERALS, FOSSILS. For Collectors, Students, Technical Schools, Colleges, &c. COLLECTIONS IN POLISHED DEAL BOXES. 25 Specimens, 5/6; 50 do., 10/6; 1oo do., 21/-; 200 do., 42/20 Coal Measure Rocks and Fossils, 12/6; do., larger, 15/-. Adapted for the Board of Education Examinations in Geology, Physiography, and Mineralogy. A large stock of Minerals, Rocks, Fossils and Microscopic Objects for selection. Specimens sent on approval. Cabinets, Geologists' Hammers, Chisels, Card Trays, Glass-capped Boxes, Models of Crystals, &c., &c. NEW CATALOGUE POST FREE. THOMAS D. RUSSELL, 78 Newgate St., London, E.C. MARINE BIOLOGICAL ASSOCIATION Sycon; Clava, Obelia, Sertularia; Actinia, Tealia, Caryophyliła, Alcy- THE DIRECTOR. NOTICE.-Advertisements and business letters for NATURE should be addressed to the Publishers; Editorial Communications to the Editor. The telegraphic address of NATURE is "PHUSIS," London. SUBSCRIPTIONS TO "NATURE." Yearly Half-yearly arterly CHARGES FOR ADVERTISEMENTS. s. d. TO ALL PLACES ABROAD:- £ s. d. £ s. d. 2 6 | Quarter Page, or Half о 0 9 a Column I 15 One Sixteenth Page, or Eighth Col. 10 O Half a Page, or a Column 3 One Eighth Page, or Quarter 5 น Column 0 18 6 Whole Page 660 £ s. d. о • The first line being in heavy type is charged for as Two Lines. Cheques and Money Orders payable to MACMILLAN & CO., Limited. GAIFFE-D'ARSONVAL MACHINE Replaces Coils, Interrupters, and Wimshurst Producing, perfectly regulating, and exactly measuring X-RAYS, HIGH-FREQUENCY CURRENTS, AND Silent in Working, Simple in Manipulation. This apparatus has been already installed by many of the chief worker in Electro-Therapeut in France and England, and is giving the very best results (vide testimonials). Replaces large Induction Coils in Laboratory and Research Work requiring High Electric Tensions or Electric Oscillations of great power and uniformity Descriptive Pamphlet gratis on application from the Sole Agents for Great Britain and its Colonies THE MEDICAL SUPPLY ASSOCIATION, 228 Gray's Inn Road, London, W.C., may be seen working. where the apparatus CROSSLEY'S GAS ENGINES RECENTLY REMODELLED. Represents K and L types, giving 3.5 H.P. and 5 H.P. respectively. Immediate Delivery for Stock Sizes GREAT REDUCTION CAS CONSUMED. Up to the end of 1904, over 50,000 engines have been delivered, representing about three-quarters of a million actual horse-power. NEW AND BEAUTIFUL PREPARATIONS IN WATSON'S UNIQUE COLLECTION. Very fine Series, illustrating the development of an Ascidian (Aspersa), 16 preparations in case... s. d. 25 0 Section through entire bud of Lily 20 Beautiful Slides of Stephanoceros with cilia extended, price according to perfection from 3/6 to Lophopus crystallinus 25 0 Groups of Diatomacea, Spicules, &c. A large variety at s. Ad 25 0 40 Vermes (Marine), various Malarial parasites-many phases Section of precious Opal, with matrix (opaque) Radium for the Microscope. Mounted on a 3 X 1 slip as a 56 Leaf of Pampas Grass-very pretty section For a Guinea a year you can have 240 Micro. Slides on hire from WATSON & SONS' Cabinets. Send for particulars. NEW. WATSON'S DIFFRACTION BUTTONS. A scientific Novelty. These buttons are made of polished steel upon which spiral lines bath inc apart are engraved. A beautifully soft radiated appearance is imparted by these lines, the colours being in the order of the Spectrum. Made in two sizes -inch diameter, 4/6 each; 6 in case for 25/4-inch diameter, 2/6 each; or 6 in case for 15/Send for WATSON'S Illustrated Catalogues of Microscopes (No. 2), Microscopic Objects (No. 3). Telescopes and Field Glasses (No. 6), Post free on application to W. WATSON & SONS, (Established) Opticians to H.M. Government, 313 HIGH HOLBORN, LONDON, W.C. Branches-16 FORREST ROAD, EDINBURGH, and 2 EASY ROW, BIRMINGHAM. Awarded 42 Gold and other Medals. THE CORRESPONDENTS' CAMERA. FOR HAND Originally made for the use of Newspaper Men in South Africa, and since used all over the World. THIS Camera has been designed for the use of correspondents, artists, and other travellers who, while requiring a Camera possessing the greatest stability, cannot spare the space for a regular field camera in addition to a hand camera. It is made of the best mahogany, carefully finished and covered with hard morocco leather, or polished in natural colour or ebonised at the same price. It is admirably adapted for Telephoto work. Owing to the use of wood instead of metal, wherever possible, this camera is lighter than many of less substantial make. EACH SIZE PERMITS OF THE USE OF THE SINGLE COMPONENTS OF A STIGMATIC OR OTHER CONVERTIBLE LENS. PRICE, including 3 Double Slides, but j 41 by 31. 6 by 41. £5 15s. 6d. £7 15s. Od. J. H. DALLMEYER, Ltd., 25 NEWMAN ST., OXFORD ST., LONDON, W. MAKERS OF THE CELEBRATED DALLMEYER LENSES. Printed by RICHARD CLAY AND SONS, LIMITED, at 7 & 8 bread Street Hill, Queen Victoria Street, in the City of Loncon, and published by MACMILLAN AND CO., LIMITED, at St. Martin's Street, i ondon, W.C., and THE MACMILLAN COMPANY, oc Fifth Avenue, New York-THURSDAY, May 11, 1905 Best and Cheapest. Engine-divided on Celluloid. 10 Rule, with Cursor, in Case, with Directions, 10/6. Useful for multiplication, division, evolution and involution, for computing strength of beams, moments of inertia, horse-power of engines. ydraulic formula, areas of circles and ellip-es, cubic contents, weights, conversion of British into metric or other systems of measurement, without Patting down a single intermediate quantity. Problems involving the ap (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 sensitive screen of the Scintilloscope, which is far more sensitive than the Spinthariscope. The Scintilloscope rivals the most delicate Electroscope as a detector of Alpha rays. The eye sees an inexhaustible shower of stars of white light, giving a very realistic idea of the ceaseless acuvity of these marvellous substances which are producing the terrific bomba ment causing this beautiful display. See NATURE, September 29, page 535. Glew's Scintilloscope Superio Lens, with Extra-sensitive Pitchblende and Polonium Screens, giving brilliant effects, Complete, 75. 6d., Post free, U.K. Foreign Postage extr, weight 2 ounces. Pieces of Pitchblende mineral, ground flat and polished, with Sensitive Radio- ctive supplies of every description, on Sale or Hire. Radiur plication of Ohm's Law of the relation between current, electro-motive F. HARRISON GLEW, urce, and resistance. Surveys by rectangular co-ordinates and set-out curves NEWTON & CO., 3 FLEET ST., LONDON. GRIFFIN'S Improved Pattern NERNST PROJECTION LAMPS with Electrical Heating Circuit. Double filament carrying 2 amps. Descriptive Pamphlet Post Free on application to JOHN J. GRIFFIN & SONS, Ltd., 20-26 SARDINIA STREET, LONDON, W.C. F. HARRISON GLEW, Radiographer 1000 (Silver Medallist, Paris, 1900), 156 CLAPHAM ROAD, LONDON, S.W. 10000 NEGRETTI & ZAMBRA ONDON 25 8000 REVISED PRICE LISTS Free by Post. The Watch Size Aneroid for foretelling weather and measur ing heights. OPTICAL CONVENTION, 1905. President: DR. R. T. GLAZEBROOK, M.A., F.R.S., Director of the National Physical Laboratory. SIR WM. DE Wiveleslie ABNEY, K.C.B., D.C.L, F.R.S. SIR W. H. M. CHRISTIE, K.C.B, M.A., F.R.S., THE RIGHT HON. THE EARL OF CRAWFORD, K.T., LL.D., F.R S. THE HON. ALBAN G. H. GIBBS, M.A., M.P., SIR HOWARD GRUBB, F.R.S. EXHIBITION OF OPTICAL & SCIENTIFIC INSTRUMENTS of British manufacture, in the large hall of the Northampton Institute, during the Convention, open daily from 12 to 10 p.m. In connection with this, a catalogue is in preparation, which will be a useful work of reference in regard to instruments manufactured in this country. The Subscription for Membership of the Convention will be five shillings. Applications for membership should be addressed to the Hon. Sec., Mr. F. J. SELBY, M.A., Elm Lodge, Teddington, Middlesex, who will be glad to furnish further particulars if desired. ADMISSION to the Exhibition, daily, ONE SHILLING, after 7 p.m., Sixpence. Tickets admitting to the Exhibition at any time while it is open, 2/6. OF ALBEMARLE STREET, PICCADILLY, W. SATURDAY, May 20, at Three o'clock, JAMES George FraZER, Esq., D.C.L., LL.D., Litt. D. First of Two Lectures on "The Evolution of the Kingship in Early Society." Half-a-Guinea the Course. TUESDAY, May 23, at Five o'clock, the Rev. HENRY G. WOODS, D.D., the Master of the Temple. First of Three Lectures on "Velazquez.' Half a Guinea. THURSDAY, May 25, at Five o'clock, Professor J. A. FLEMING, M.A., D.Sc., F.R.S. First of Three Lectures on "Electromagnetic Waves.' Half-a-Guinea. Subscription to all Courses in the Season, Two Guineas. BIRKBECK COLLEGE, BREAMS BUILDINGS, CHANCERY LANE, E.C. HISTORY OF CHEMISTRY. A Course of Nine Lectures will be given by Dr. J. E. MACKENZIE ON Saturdays, commencing May 27, at 12 noon. Accommodation and apparatus provided for research in either Pure or Applied Chemistry and Physics, and Engineering, in rooms specially adapted for this purpose. Full particulars at the Institute or sent on receipt of postcard. At the SOUTH-WESTERN POLYTECHNIC, Hill: Manresa Road, Chelsea, S. W., Day College Courses of thirty hours per week are conducted in preparation for the London University Degrees of B.Sc. in Mechanical and Electrical Engineering, in Chemis try, Physics and the Natural Sciences. The composition fee for the Session of three terms, 1904-1905, is £15. These Courses are recog nised for "Internal Students" of the University, and consist of lecture and laboratory instruction. The Courses are conducted by:MECHANICAL ENGINEERING, W. W. F. Pullen, A. Macklow Smith ELECTRICAL ENGINEERING, A J. Makower: CHEMISTRY, J. B. Coleman, J. Crocker, and F. H. Lowe: MATHEMATICS and PHYSICS, S. Skinner, W. H. Eccles, J. Lister and L. Lownds; BOTANY, H. B. Lacey and T. G. GEOLOGY, A. J. Maslen. In the evenings similar Courses will be conducted, but at £2 per Session. Also TECHNICAL DAY COURSES of three years' duration are arranged as a preparation for the Engineering, Electrical and Chemical and Metallurgical pro fessions. The Laboratories and Workshop are open for RESEARCH under the direction of The Principal and the Heads of Departments. Further particulars may be obtained on application to The SECRETARY, who will send either the Day College Prospectus and Calendar or the Evening Class Prospectus for 3d. The Prospectuses may be had at the Office for id. each. COACHING (THEORY AND PRACTICE) In BIOLOGY, BOTANY, CHEMISTRY and PHYSIOLOGY for MEDICAL EXAMS. Especial Course of Instruction in THERAPEUTICS, PHARMA COLOGY and MICROSCOPY for INSTITUTE OF CHEMISTRY EXAM. Mr. FREDERICK DAVIS, The Laboratories, (Registered in Column B (Advanced Education). Teachers Registration Council, Board of Education, S.W.), 49 and 51 IMPERIAL BUILDINGS, LUDGATE CIRCUS, E.C. THE AGENT-GENERAL for the CAPE OF GOOD HOPE has been instructed to receive applications for the vacant post of PROFESSOR OF ZOOLOGY to the SOUTH AFRICAN COLLEGE, CAPE TOWN, up to June 1 next. Candidates must be under 35 years of age, and their applications should be supported by copies of testimonials and a medical certificate. The salary offered is £500 per annum on appointment, £600 per annum after three years' service, £700 per annum after ten years' service, together with a merit grant of £75 per annum after five years, increasing to 100 after ten years. An allowance of £50 will be made to cover the cost of the journey to the Colony. The accepted Candidate is to assume duty in Cape Town during the first week in July, or so soon thereafter as possible. 100 Victoria Street, London, S. W., May 2, 1905. TO SCIENCE MASTERS, especially those taking ELECTRICITY as a special subject. Wanted by July 1 next for important College, well-qualified Master for Electricity. One who has had some experience in the organisation of the work of a local Technical Instruction Committee. Salary, £150 to £200 per annum. Candidates for the above and those seeking posts for the term commencing in September next should apply forthwith, giving details as to qualifications and enclosing copies of testimonials, to GRIFFITHS, SMITH, POWELL & SMITH. School Agents (Estd. 1833), 34 Bedford Street, Strand, London. Scientific Assistant and Mechanician requires responsible and progressive appointment (works or private). Mentioned in original research, Chem. and Physics. Highest refs. NEWCASTLE-UPON-TYNE. ENGINEERING DEPARTMENT. The Council invites applications for the post of DEMONSTRATOR in MECHANICAL ENGINEERING. Duties to begin on October 1, 1905. Stipend commencing at £150 per annum. Apply, with one set of testimonials, en or before June 8, 1905, to the undersigned, from whom full particulars may be obtained. F. H. PRUEN, Secretary. ARMSTRONG COLLEGE, NEWCASTLE-UPON-TYNE. DAY TRAINING DEPARTMENT. The Council invites applications for the post of MISTRESS of METHOD and LECTURER in EDUCATION. Stipend commencing at 150 per annum. Applications, with one set of testimonials, must be sent to the undersigned not later than June 8, 1905, from whom full partulars may be obtained. F. H. PRUEN, Secretary. THE GLASGOW AND WEST OF SCOTLAND TECHNICAL COLLEGE. The Governors invite applications for a LECTURESHIP in CIVIL ENGINEERING which it is proposed to establish. The salary attached to the post is £250 per annum, and the lecturer must be prepared to give his whole time to the College. Applications and testimonials must be sent not later than May 31 to the SECRETARY, 38 Bath Street. Glasgow. The "N" Fellowship, tenable at Cambridge and open to former science students of Newnham and Girton Colleges, will be vacant in the autumn. The holder is required to conduct onginal research in science during her tenure of the fellowship, with preference to the chemical physiology of animals and plants. Applications must be sent in by June 8 to the PRINCIPAL OF NEWNHAM COLLEGE, from whom further particulars may be obtained. FOR DISPOSAL, an Exceptional Bargain, ROSS BINOCULAR MICROSCOPE with Mechanical Stage and Sub stage, 3 Eyepieces: ", 1", 2" and 4" Objectives, Condensing Lens; Polariscope; Camera Lucida and many accessories. Cost over 4. Condition as new. For disposal owing to death_of owner. 1. west price £20 to an immediate purchaser. No dealers.-For further particulars address " F. C. S.," c/o Fletcher, Fletcher & Co., Holloway, London, N. Metallurgical Laboratory, well equipped for experimental work, to let at low rent. One minute from Station. Fifteen minutes to City. Apply MARSHALL & Co., Campbell Works, Stoke Newington, N. (close to Station, G. E.R.). Tel., 79 Dalston. 18-inch Apps-Newton Coil for sale, in perfect condition. No trace of oxidation on the vulcanite. G. BOWRON, 57 Edgware Road, W. Astronomical Telescope, with 4 in. clear aperture, altazimuth stand, day and 4 astronomical eyepieces, price only £17; others cheaper.-Microscopes, second-hand by ZEISS, with substage and Abbé condenser, eyepieces, 2 objectives and triple nosepiece, for £9. Another by PISCHER, with mechanical stage, substage-condenser and Iris-daphragm, eyepieces, 3 objectives, viz.: 1", ", &" oil immersion. price only £6 10s. Another by PowELL & LEALAND, with mechanical stage, tage-condenser, and seven objectives all "P and L," offered for £10. Binocular Microscope by SWIFT, cost £40, offered at £10. other by STEWARD, with mechanical stage, 2 objectives, double nosepiece, 26. Assay Balance by OERTLING, 6 in. beam, double columns, sensitive to milligram, double rider. ccst £25, offered at £6. Others in Stock. 20 ft. Hydrogen Cylinder (charged), price £1. Scientific Lantern Slides on every subject at 5d. each. Microscope Slides on approval at 4d, each. Rev. H. MILLS, Greenside, Kendal. An Engraved Real Size. AN ACHROMATIC COMBINATION. COMBINING THE DEFINITION OF A MICROSCOPE WITH THE PORTABILITY OF A POCKET LENS. "If you carry a small Platyscopic Pocket Lens (which every observer of Nature ought to do)."-GRANT ALLEN, in Knowledge. "I have long carried one of these instruments and found it invaluable."--JOHN T. CARRINGTON, Editor of Science Gossip. The Platyscopic Lens is invaluable to botanists, mineralogists, or entomologists, as it focuses about three times as far from the object as the Coddington Lens, and has a field unequalled for flatness, allowing opaque objects to be examined easily. It is made in four degrees of power, magnifying respectively 10, 15, 20, and 30 diams.; the lowest power, having the largest field, is the best adapted for general use. Mounted in Tortoiseshell, magnifying 10, 15, 20, or 30 diameters, either power... ... In Nickelised German Silver, either power Combinations of any two powers, in Tortoiseshell Ditto Ditto in Nickelised German Silver ILLUSTRATED DESCRIPTION SENT FREE. JOHN s. d. 15 O 17 6 27 6 32 6 BROWNING, MANUFACTURING OPTICIAN, 78 STRAND, LONDON, W.C. DO YOU WISH UP TO DATE in Scientific Demonstrating ? ALL ACCESSORIES SUPPLIED. ARC LAMPS, RESISTANCES, MARA. KERSHAW, Dorrington St., Leeds. CONTRACTOR TO H.M.'s GOVERNMENT. Rare Chemicals, Rare Metals, Rare Minerals 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. |