January, 1915. 



KNOWLEDGE. 



FOR 



CONDENSERS 



AND 



RHEOSTATS 



OF 



British Manufacture 



WRITE TO 



ISENTHAL & GO. 



(Department 2] 



DENZIL WORKS, NEASDEN, LONDON,N.W. 



Ct'fit'iic/ars to the Adiitiialty^ ll'ai\ huiia, and 

 Colonial Offices, &'c. 



BROWNING'S SPECTROSCOPES. 



THE MINIATURE SPECTROSCOPE. 



These instruments will show many of the Frannhofer lines, the 

 bright hnes of the metals and gases, and the absorption bands in 

 coloured gases, crystals or liquids, and may be used for showing 

 many of the leading experiments in Spectrum Analysis. They are 

 made with combinations of three prisms at prices from 20s. to 

 3Ss., or with five prisms, .nivmg much greater dispersion, and 

 therefore showing the lines and bands more distinctly, at prices 

 from 25s. 6d.' to 70s. 



BROWNING'S MINIATURE SPECTROSCOPE with MICROMETER 



Hv means of the Photographed Scale the position of any of the 



lines may be recorded, and the Comparison Prism enables two 



spectra to be seen and comparetl in the held of \'ie\v. 



Price in IVIopocco Case, £3 10 O. 



TABLE SPECTROSCOPES AND SPECTROMETERS, 



HIGH-POWER DIRECT VISION SPECTROSCOPES. 



RAINBAND SPECTROSCOPES, MICRO - SPECTROSCOPES 



AND STAR SPECTROSCOPES. 



" Hovw to Work vwith the Spectroscope." KyJOHN I'.rowmn',, 



P.R.A..S., Etc., 4tii Ktiiliuii, ^-iilirrly reuritleii ;uul revised. Price 9d.. or with 

 CL'loiwed Cliait of 14 Spcctr.i. Is. 6cl. Post free. 



Man'f'g 146 STRAND, and I flMnntlJ 



JOHN BROWNING 



Optician, 72 New Oxford St. 



Tul. N'ci. 



Mil Central. 



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SIXPENCE WEEKLY. 



Readers of "Knowledge" may like 

 to have their attention directed to 

 the following topical articles which 

 have appeared in recent issues of 

 NATURE: 



"Openings for British Chemical 



Manufacturers" {Septciiil)Li- 17): 

 "Glass for Optical Purposes" 

 {October II: "The Cultivation of 

 Medicinal Plants in England " 

 [October 151: "The Sea Fisheries 

 and the War" (October 221: "The 

 Place of Science in Industry ' 

 (Xo-cciiibcr 121, "The Supply of 

 Pitwood ' ; " Effects of the War on 

 Scientific Undertakings" {December 

 nil " High Explosives in Warfare" 

 i!)eceiiil)er 2^i , "Optical Glass 

 and Scientific Instruments : United 

 Kingdom Imports and German 

 Exports" ijiuiuary 7i 



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