STANDARD BAROMETER Registered Design No. 420,297. As will be seen by the illustration, this Barometer is built on original lines. By the absence of the ordinary tubular enclosures (in the usual form of instrument) the mercurial column is FULLY EXPOSED to view, NO SHADOWS are thrown upon the column, and therefore an extremely accurate and instantaneous reading is made possible. The scales being graduated upon the flat side pieces the DIVISIONS AND FIGURES ARE ALWAYS IN VIEW, and the vernier is very much more legible than in the ordinary tubular patterns. The bore of the tube is 0.5 inch. The scales are graduated in inches and millimetres, and, by means of the verniers, are capable of being sub-divided to read to 0.002 inches and 0°1 m/m. The attached Thermometer on the body of the instrument is graduated in Fahrenheit and Centigrade scales. It is the BOLDEST Standard Barometer made. The PRICE IS LOWER than that of any other form of Standard Barometer of the same dimensions. It yields readings equally close as the highest priced instruments. Price complete, mounted on handsome Polished Solid Mahogany Board, with Brackets for Suspension, and Opal Glass Reflectors, SMALLER SIZE, "THE STUDENTS," designed for Schools for demonstration work, and small private Observatories; bore 25; reading to '01 inch and 1 millimetre. £3 7s. 6d. Sole Manufacturers and Proprietors of the Regd. Design: NAT. TEL.: 1981 Holborn. Estd. 150 years. N. B. If any difficulty be found in securing any of our Instruments through your Dealer, kindly communicate with us. METALLURGICAL LABORATORIES. Sardinia Street, London, W.C. WAVE-LENGTH SPECTROSCOPE (LARGE MODEL.) Measures wave-lengths direct to an accuracy of 1 Angström unit (one ten-millionth of a metre) from W. L. 3888 to W.L. 7724. SPECIAL ADVANTAGES. The Collimator and Telescope are rigidly fixed at right angles, thus the instrument will stand in a corner, is always ready for use and in adjustment. The wave-lengths can be read off by the observer without moving from his place. The object glasses and prism are large (1" clear aperture), which enables the faintest visible lines to be seen. The eyepiece has a bright pointer for measuring the W. L. of bright lines on a dark field. Means are supplied of very simply setting the Zero, although on account of the great rigidity and careful construction throughout it may be used for many months without any setting being needed. ADAM HILGER, Ltd., 75a Camden Road, London, N.W. AWARDED GOLD MEDAL ST. LOUIS EXHIBITION, 1904. ILLUSTRATED LIST ("A") OF SPECTROSCOPES AND SPECTROSCOPIC ACCESSORIES ANY KIND OF SCIENTIFIC INSTRUMENT MADE TO ORDER. Prompt Attention to all Orders and Inquiries. EXCEPTIONAL TERMS TO COLLEGES, INSTITUTIONS, &c. Quotations submitted for Laboratory Outfits or Single Instruments. THERMOMETERS FOR STUDENT WORK A SPECIALITY. Catalogues Post Free. (State which required.) 8, 9, & 10 HATTON GARDEN, LONDON. 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SECOND-HAND, large and ever-changing stock. Van Heurck, new, others including Objectives, Condensers, Polariscopes, &c., by Watson, Ross, Powell and Lealand, Beck, Pillischer Reichert, Leitz, &c. Prismatic Binoculars, Lantern Slides, Mounting Materials. Lists. Mr. HERBERT CLARKE, 104 LEADENHALL STREET, LONDON. Tel.-1316 Central. ROCKS, MINERALS, FOSSILS. For Collectors, Students, Technical Schools, Colleges, &c. COLLECTIONS IN POLISHED DEAL BOXES. 25 Specimens, 5/6; so 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 NEW CATALOGUE POST FREE. THOMAS D. RUSSELL, 78 Newgate St., London, E.C MICROSCOPICAL PETROGRAPHY. Gentlemen interested in the above study are invited to send to JAMES R. 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New Catalogue (102 pp.) just issued, post free. LANTERN SLIDES of Scientific Subjects, from 6/- per dozen. Also Hand Painted from 1/3 to 5/- each. Slides from Prints, Drawings, Photographs, &c., a Speciality. MARINE BIOLOGICAL ASSOCIATION Sycon; Clava, Obelia, Sertularia; Actinia, Tealia, Caryophyllia, Alcy- LANTERN THE DIRECTOR. SLIDES.-Orchids, Cacti, Palms, Insectivorous Plants, &c.-For lists apply L. FARMAR, 6 Mortlake Terrace, Kew. PHOTOMICROGRAPHY for Publishers, Lecturers, Manufacturers, and general scientific research. Good work, moderate charges.-SAXBY, 91 Penny Lane, Sefton Park, Liverpool. NOTICE.-Advertisements and business letters for NATURE should be addressed to the Publishers; Editorial Communications to the Editor. The telegraphic address of NATURE is "PIUSIS," LONDON. Represents K and L types, giving 3.5 H.P. and 5 H.P respectively. Immediate Delivery for Stock Sizes GREAT REDUCTION GAS CONSUMED. Up to the end of 1904, over 51,000 gas and oil engines had been delivered, representing about threequarters of a million actual horse-power. CROSSLEY BROS., LTD., OPENSHAW, MANCHESTER NEW MICROSCOPIC SLIDES From the New Issue of W. WATSON & SONS' No. 3 CATALOGUE, just published. Post Free on application. s. d. 7 6 Send for Special Descriptive List. Section of Brazilian Quartz, showing cavities containing fluid. Trypanosoma Brucei (Tsetse Fly disease) 25 0 40 ... 3 6 Set of 5 Slides of the Garden Spider, showing different stages of 76 Blood-sucking Maggot (from the Congo) Fly hatched from above, Auchmeromyia luteola Eggs of Emperor Moth, fertile and sterile, on 1 slide Leg of Flea, showing muscular structure Set of 16 Slides illustrating the development of an Ascidian 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. DALLMEYER'S TELE-PHOTO. LENSES & ATTACHMENTS Printed by RICHARD CLAY AND SONS, LIMITED, at 7 & 8 Bread Street Hill, Queen Victoria Street, in the City of London, and published by MACMILLAN AND CO., LIMITED, at St. Martin's Street, London, W.C., and THE MACMILLAN COMPANY, 6t Fifth Avenue, New York.-THURSDAY, August 31, 1, |