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A WEEKLY ILLUSTRATED JOURNAL OF SCIENCE. 



" To the solid ground 

 Of Nature trusts the mind which builds for aye." — Wordsworth. 



No. 357,;, Vol. 102] THURSDAY, FEBRUARY 20, 1919 



[Price Ninepence. 



Registered a* a Newspaper at the General Post Office.] 



[All Rights Reserved. 



BALANCES & WEIGHTS 



Graphite-Selenium Cells 



FOURNIER D'ALBE'S PATTERN. 



Great Stability and High Efficiency. 



With a sensitive Se surface of 5 sq. cm. and a voltage 20 the 

 additional current obtainable at various illuminations (in 

 metre-candles) is : — 



For particulars and prices apply to the Sole Agents : 



John J. Griffin & Sons, 



Makers of Physical and Electrical Apparatus, 



Kemble Street, KINGSWAY, 

 LONDON, W.C. 2 



REYNOLDS & BRANSON, Ltd., 



Chemical and Scientific Instrument Makers to His Ma|esty's 



Government (Home and Overseas Dominions). 



LABORATORY FURNISHERS and MANUFACTURING CHEMISTS. 



WORKS AND OTHER 



LABORATORIES 



equipped 



with Benches, Fume 



Chambers, Apparatus 



and Chemicals. 



■>i" 



d quotations 

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BRITISH - MADE Glass, Porcelain, 



Nickel Ware, and Filter Papers. 



Apparatus in Glass, Metal, or Wood made 



to customers' own Designs. 



CATAZ.OGVE8 POST FREE. 

 Enquiries lor Technical Chemicals in quantity solicited. 



14 COMMERCIAL STREET, LEEDS.' 



BECKMANN THERMOMETERS 



With 6 degrees Centigrade divided 

 into 001° C, are now made 

 throughout at our own works. 



NEGRETTI & ZAMBRA 



38 HOLBORN VIADUCT, E.C. 1 

 5 LEADENHALL ST., E.C. 3 

 122 REGENT STREET, VV. 1 



LONDON. 



