A WEEKLY ILLlSlRAli'lJ JOURNAL OF SCIENCE 



" To the solid ground 

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



No. 1856, Vol. 72] 



THURSDAY, MAY 25, 1905,, 



[Pric e Sixpence 



Registered as a New5;paper at the General Post Offici 



[AU Rights are Reserved. 



THE NEW "ADIX" CALCULATOR. 



'I be neatest, simplest, smallest and cheap>,^t calculating machine ever 



designed. For adding up columns of figures rapidly and accurately. Can 



be used by anyone. " A necessity for all who have to add." Made 



entirely in steel and aluminium. 



Price 31/6 complete in leather case 6" • 3?" •- 1". 



IVE-WTOPa^ SC CO., 



Scientific Instrument Makers to H M. the King, H.R.H. the 

 Prince of Wales, and the Government. 



3 FI^EEII' STR.EET, X.O:PJDOPir. 



PHOTOGRAPHIC LENSES. 



A SIMPLE TREATISE. 

 By CONRAD BECK and HERBERT ANDREWS. 



1/-, Post Free 1/3. 



This somewhat difficult subject is made clear without 

 the use of mathematics. 



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



PRACTICAL NOTES ON 



TELEPHOTOGRAPHY. 



Free on application to 



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



RESONANCE COIL 



of thie 



NEW HIGH POTENTIAL APPARATUS. 



wm- See also page xxxiii in this issue. 

 ISENTHAL & CO., 85 Mortimer St., London, W. 



NEGRETTI & ZAMBRA'S 



ANEROID 

 BAROMETERS. 



NEW ILLUSTRATED AND 



REVISED PRICE LISTS 

 Free by Post. 



The Watcti Size 

 Aneroid for foretelling 

 weathsr and measur- 

 ing heights. 



38 



Holborn Viaduct, 



45 Cornhill; 



tti3 Regent Street. 



