January, 1915. 



KNOWLEDGE. 



WATSON'S 

 BRITISH-MADE 

 MICROSCOPES 



Special arrangements have been made 

 for prompt supplies of 



Watson's Microscopes and Accessories 



to replace those of Continental mahe that are 

 unobtainable in consequence of the War. 



NO INCREASE IN PRICES 



The 24^.'' Edition of Watson's Catalogue 

 of lyiicroscopes and Accessories, 



192 pages, has just been issued, and contains new 

 models, new accessories, and many improvements. 



Make Your Monocular into a Binocular 



Microscope, it can now be done by the 

 use of a WATSON'S New 



"BICOR" 



BINOCULAR 



ATTACHMENT 



(Patent applied /cr) 



It offers many advan- 

 tages, among which are 

 the following : — ■ 



It is attached to a 

 Monocular Microscope 

 in the same way as a 

 Revolving Nose-piece. 



Tube length can be 

 varied and interocular 

 width adjusted to any 

 extent. 



Brilliance of image in 

 both tubes the same. 



No sacrifice of defi- 

 nition is observable. 



The above, with many 

 other important improve- 

 ments ajid introductions, 

 including a series of 



APOCHROMATIC 

 OBJECTIVES, 



are to be found in Wat- 

 son's newly - published 

 Catalogueof Microscopes. 



Pest free on application. 



No. 2. 

 " Bicor " Binocular Attachment. 

 Screw to attach to Monocular Body. 

 ' Screw to receive Objectives. 

 Screw to adjust for width of eyes. 



W. WATSON & SONS, LTD., 



Gonttactors to ti./B. Govctnnicnts, 

 313 HIGH HOLBORN, LONDON, W.C. 



Branches : 

 16 Forrest Road, Edinborgh ; 196 Great Portland Street, London, W. 



DetAts : 



i Easy Row, Birmlofibam ; 78 Swanston Street, Melbourne, Australia; 



212 Notre Dame Street West, Montreal, Canada. 



Optical Works— HIGH BARNET, HERTS. ESTABLISHED 1837. 



BECK'S TELESCOPES 



Telescope Obiect Glasses, 



Portable and Naval 



Telescopes, 



Diffraction 



Spectroscopes, 



Snr>eyinS instruments 



DESCRIPTIVE CATALOGUE 



Fost Free oti application to — 



R.&J. BECK, Ltd., 68, GORNHILL, LONDON. 



DENT'S CLOCKS 



WATCHES AND CHRONOMETERS 



FOR SCIENTIFIC USE. 



Sidereal op Mean Time Clocks for 

 Observatories, £21 and upwards. 



THREE GRAND PRIZES 

 AND ONE GOLD MEDAL 



FRANCO -BRITISH EXHIBITION. 



The only Grand Prize awarded 

 to a British Firm for Watches, 



Clocks and Chronometers. 



The only Grand Prize awarded 

 for Astronomical Reg;ulators. 

 Chronographs, and Ship's 



Compasses. 



TRADE MARK 



61, STRAND, and 4, ROYAL EXCHANGE, LONDON. 



Telephone .\o. 61 City. 





ADVERTISEMENT RATES. 



Whole Pago £6 6 O 



Half Page 3 5 O 



Quarter Page 1 IS O 



One-Eighth Page 18 6 j-b) 



One Sixteenth Page O tO O S; 



Per Inch, NarroMr Column O 7 Ol 



Half „ „ „ O 4 q' 



Discounts for Series of Insertions and Rales for Special Positions, when 



Vacant, on application to The .\dvertisement Manager, 

 Knowledge Office, Avenue Chambers, Bloomsbury Square, London, W.C. 



COCOA 



EARTH 



GUARANTEED ABSOLUTELY PURE SOLUBLE COCOA ONLY. 



