A WEEKLY ILLUSTRATED JOURNAL OF SCIENCE. 



" To the solid ground 

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



No. 2260, Vol. 90] 



THURSDAY, FEBRUARY 20, 1913 



[Price Sixpence 



Newspaper at the General Post Office. 



(All Rights Reserved. 



Elbow Polariseope, for illustrating Iht; various phe- 



noniena of polarized light, with polarizing glass plates, 



prism atid lenses, mounted in brass, with rack adjustment 



to focus tube, in case, complete, £7 Vs. 



\\IGMOr-;E ST., LONDON, 



BECK'S FOCOSTAT LENS 



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



REYNOLDS & BRANSON, Ltd. 



(AWARDED GRAND PRIX, TURIN, 1911.) 



SPECIAL APPARATUS 

 for Consterdine & Andrews' 

 'PRACTICAL ARITHMETIC." 



Set "A," I20 models, 



£15 



Set " B," 75 models, 



£0 16 6 



^Descriptive List on 

 Appfiinfion. ) 



Special Apparatus for Mackenzie and Forster's 



Theoretical & Practical Mechanics & Physics. 



Detailed Catalogue on Application. 



CATALOGUES POST FREE. 



Scientific Apparatus and Chemicals. Apparatus for 



Teaching- Mechanics, Machine and Building Construction. 



Optical Lanterns. Photographic Apparatus. 



14 COMMERCIAL STREET, LEEDS. 



The 



"Seathwaite" 



Rain Gauge ^^ 



has a 5-inch 

 diameter funnel, 

 and a capacity of 

 30 inches of rain. 

 It is constructed to 

 prevent evapora- 

 tion and freezing. 

 The gauge for 

 outlying districts. 

 NEGRETTI 

 & ZAMBRA, 

 Holborn Viaduct, 



London, E.G. 

 45 Cornhill, E.G. 

 122 Regent St., W. 



