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^^Tnstit^ 



MAY 16 1913 



A WEEKLY ILLUSTRATED JOURNAL OF SCIENCE.\X 



" To the solid ground 

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



No. 2270, Vol. 91] 



THURSDAY, MAY 1. 191 3 



[Price Sixpence 



Newspaper at the Ge 



[All Rights Reserved. 



COMPLETE SALE OF 



Physical & Philosophical 



APPARATUS. 



Also Shop Soiled and Secondhand 

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Full Catalogue (14 pages) ready in a 

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NEWTON & CO., 

 72 Wigmore Street, London, W. 



Established 200 Years. 



STUDY 



THE LENS 



It is the Key to Success in Photography. 



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" PHOTOGRAPHIC LENSES : 



A SIMPLE TREATISE." 



35° P a ges, 44 plates, numerous diagrams and 

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R. & J. BECK, Ltd., 5?„:=22S?E£: 



LEITZ PRISM BINOCULARS 



Increased light-gathering power. Larger field of view, 

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Descriptive Price List Post Free. 



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since the year 1857. 

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NEGRETTI & ZAMBRA 



Scientific Instrument Makers, 



Holborn Viaduct, London, E.C. 

 City Branch : 45 Cornhill, E.C. 

 West End: 122 Regent St., W. 



