A \v1':ekly illustrated journal of science. 



'■ Tn the soli,! ipvuiid 

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



X-RAY "FOCUS" TUBES. 



The " Focus" Tubes made by Newton & Co., in accordance 

 with ihe experiments conducted in the Chemical Laboratory at 

 King's College, are still unequalled for rapidity and definition. 



Price 30s. each. 



The above are suitable for Coils giving 2" spark and over. 



Special "Focus" Tubes, 42s. each. 



The above are suitable for Coils giving from 7" to lo" sparks. 



'* The definiiion given by your focus tubes is excellent." — Prof. Oliver 

 J. LonCE, Unh'trsity College^ Liverpool. 



*' Your focusing lube has worked very well, and .is soon as you have 

 another similar one that you can spare me 1 shall be glad to have it."— 

 Prof. A. Schuster, Tht Owens College, Manehester. 



"We ha\e got excellent results with the focus tubes. —Prof. W. 

 Heaton, Unh>ersity College, Noltinglmvt. 



'* 1 he focus' tube you sent eives remarkably sharp shadows." — Prof. A. 

 S. BuiLER, The Unhersity,St. Andre^us. N.B. 



"I have tried a very large number of vacuum tubes sold by different 

 makers for Ihe purpose of giving the X-rays, and find your ' focus tubes ' to 

 be far and away superior 10 anything as yet in the market." — Prof. W. F. 

 Barrett, Foyal College of Science, Dnblin. 



" Les rdsullais sont merveilleux."— Dr. Henri van Helrck, Jariiin 

 Botanique H'Anvers. 



Sole !\L\kers : 

 IW 13 "W T O IW ^B CO. 



3 FLEET STREET, LONDON. 



BROWNING'S SPECTROSCOPES. 



The Stude 



Specti 





irkmanship ; ' 

 utes ; the slit 

 spectra can be 



is n prism of extremely dense glass, of very 

 le is divided, and reads with a vernier tO' 

 shed with a reflecting prism, bj' means of 

 in the field of view at the same time. The 

 n the Solar Spectrum, or the yellow Sodium 

 lines di-itinctly. With a slight alteration of the adjustments, the instrument 

 can be used for taking the refractive and dispersive powers of solids or 

 liquids. The Student's Spectroscope is the best instrument for the Labora- 

 tory and for all general work in Spectrum Analysis. 



PRICE, COMPLETE IN CABINET, £6 lOs. 01 



Illnsfraieii Catnlogite of Spectroscopes, post free. 



Helium ami Argon Spectrum Tubes Now A'cady, iOs. 6d. each, j JOHN BROWNING. 63 STRAND, LONDON, W.C 



BECK'S MICROSCOPES, negretti & zambra. 



25 A.— THIS MODEL, with 

 i-in. and J-in. Object Gla,s.ses, 

 Two Eyepieces, and packed 

 in I'olislied Mahogany Case, 



£6 lOs. 



No. 25B.— THIS MODEL, with 

 ?-in. and J-in. Object Gla.sses, 

 Two Eyepieces, and packed 

 in I'olished Mahogany Case, 



£7 5s. 



SOLE MAKERS OF 



JORDAN'S (PATENT) SUNSHINE RECORDER. 



STAND No. 25. 



29B. — The addition of Abbe 

 Condenser to 25B with Iris 

 Diaphragm and Focussing 

 and Swinging Adjustments, 

 £8 15s. 



^^C//.L PARTICULARS FREE on APPLICATION to 



R. & J. BECK, Ltd., 68 cornhill, London, e.c. 



New Simplified Model, 

 adjustable for any 

 latitude, and tho- 

 roughly efficient. 

 Price £1 7s. 6d. 



Sensitised Charts^ 

 5s. per 100. 



NEGRETTI 

 ZAIVIBRA» 



Scientific Instrument 

 Makers to the Queen, 



38 HOLBORN VIADUCT. 



Branches — 45 Corn'hm.l, 

 122 Regent Street,. 



Lo.NDON. 



ILLUSTRATED DESCRIPTION POST FREE. 



Telephone No. 6=83. Telegraphic .address, " Negretti, London.' 



