NATURE 



[February 27, 1919 



Analytical Reagents 



Chemicals characterised by the letters " A. R.' They 

 are supplied in bottles sealed with a neck-band, which 

 should be unbroken when the package is received, and 

 bearing a label, of which the following is a specimen. 



Volumetric Solutions and Pure Chemicals 



for Standardisation Purposes. 



Test Solutions, Special Reagents, 



Indicators and Test Papers. 



Stains and Reagents for Microscopic Work 



Catalogue on application to— 



THE BRITISH DRUG HOUSES, Ltd., 



(Chemical Department), 



22 to 30 Graham Street, City Road, 

 LONDON, N. 1. 



Chemical Works: Wharf Road, London, N. 1. 



SMALL ELECTRIC LAMPS 



FOR ALL 



SCIENTIFIC PURPOSES. 



Jlpply to the MANUFACTURERS : 



A. C. COSSOR, Ltd., 



Aberdeen Works, Aberdeen Lane, 

 Highbury Grove, London, N. 5. 



Telephone: North 1385 Telegrams: "Amplifiers, Phone, London 



DINT Si. CO., S^tci., 



Clock, and Chronometer Makers. 

 Special Appointment to H M. the King. 

 he Qreat WeBtmttuter Clock. Big Ben. Maker* < 



at the Koya] 



i World. 



Only Ad'IrrHtf*- 



DENT'S ASTRONOMICAL CLOCKS 



SIDEREAL OR MEAN TIME CLOCKS FOR OBSERVATORIES. PRICES ON APPLICATION 



f DENP^ 



61 STRAND, ' "'" 



AND 4 ROYAL EXCHANGE, LONDON. 



q 3 Grand Prises and r Geld Medal Franco-British 



Exhibition. 



WATKINS & 00NCASTER, 



Naturalist* and Manufacturers of 



CABINETS AND APPARATUS 



FOR COLLECTORS OF INSECTS, BIRDS' EQBS AND SKINS, 



MINERALS, PLANTS, Ac. 



N.B. — For excellence and superiority of Cabinets and Apparatus 



references are permitted to distinguished patrons, Museums. Colleges, *c 



A LAROB STOCK OF INSECTS, BIRDS' BOOS AND SKINS, 



speciality. Objects for Nature Study, 

 Drawing; Classes, &c. 



Birds, Mammals, &e., Preserved and Mounted by First-class 



Workmen true to Nature. 

 All Books and Publications (New and Second-hand) on Insects, 



Birds' Eggs, &c, supplied. 



86 STRAND, LONDON, W.C. 2. 



(Five Doors from Charing Cross.) 

 FULL CATALOG UK POST sT RKK 



FOR SALE 

 SET OF METALLURGICAL OBJECTIVES 



By W. WATSON & SONS 



,'," oil Immersion, 130 N.A., ji", an, I 



ASTRONOMICAL TELESCOPES 



4i-in. NEGRETTI & ZAHBRA, on equipoise stand, finder, 

 3 astro, and I day eyepieces, horizontal movement by 

 Hooke's joint, vertical rack attachment .. £45 



3-in. AITCHiSON, 1 astro, and 1 day eyepieces, pillar and 

 claw stand ..." £7 15 



WANTED 



Microscopes, Telescopes, Drawing Instruments, &c. 

 CLARKSON'S, 338 High Holborn, London, W.C. 1 



(Opposite Grays Inn Road.) 



WANTED.— Hilger's Quartz Spectrograph, 



also compact Induction Coil, good 4" spark. — C. J. S. Bakbb, 

 28 Emperors Gate, South Kensineton. 



PETROLOGICAL MICROSCOPE by 



Stanlev, tn good condition, with i-inch, g-inch, and ^-inch objectives. 

 Polarizer and analyser. In case con-plete, with two eyepieces. Price 

 40 guineas.— John Browning, 146 Strand, W.C.2 



MICROTOME — Reichert — very complete, 



new condition, with knives, Xc. ; also Ether Freezing Machine. 30 

 guineas cash.— John Bkowmng. 146 Strand, London. 



SCIENTIFIC APPLIANCES for Electrical, 



Magnetic, Static, Optical, and Philosophical Apparatus and 



Materials. New and Second-hand P.O. Instruments and parts by 



high-class makers one-third cost. Achromatic Lenses, Prisms, 

 and experimental sundries. Static Machines, Colls, Pneu- 

 matic apparatus, and parts. Fifty years' experience. Call and see 

 or write for information. Our war-time list two stamps.— 

 SCIENTIFIC APPLIANCES (Dale & Hollins), 11 and 13 Sicilian 



w. 



OLD PLATINUM, GOLD 



Dental Alloy, Scrap, &.c. 

 Purchased tor Cash or Valued, 



SPINK & SON, Ltd., 



17 & 18 PICCADILLY, LONDON, W.I. 



E8T. t772. 



Fine Jewels or Plate also purchased or valued. 



JAMES R. GREGORY & Co. 



Are open to purchase fine 



Crystallised Minerals 



Address : 139 Fulham Road, South Kensington, S.W. 3. 



Telephone : Telegrams : 



