A WEEKLY ILLUSTRATED JOURNAL OF SCIENCE 



" To the solid ground 

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



i No. 1864, Vol. 72] 



THURSDAY, JULY 20, 1905 



[Price Sixpence 



Registered as a Newspaper at the General Post Office.] 



NEWTON & CO., Opticians to the King, 

 3 ir'uEiEiT stre:e:t, i..op*i>c»n. 



PHOTOGRAPHIC LENSES. 



A SIMPLE TREATISE. 



By CONRAD BECK and HERBERT ANDREWS. 



X/-, 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 COHHHIIL, lOllDOB, 



REYNOLDS & BRANSON, L° 



LABORATORY OUTFITTERS and 

 SCIENTIFIC INSTRUMENT MAKERS. 



« I C 



14 COMMERCIAL STREET, LEEDS. 



NEGRETTI & ZAMBRA'S 

 LONG RANGE 



BAROMETERS. 



and 



THE GLYCERINE BAROMETER. 



This Barometer has a tube containing both Mercury a: 

 Glycerine. The lighter specific gravity of the la 

 the difference in the bore of the lube in which it rises and 

 falls increases the scale to about S inches for each inch of 

 the ordinary mercurial column. 



By means of this interesting instrument the smallest 

 variations in the atmospheric pressure are quite notice- 

 able, differences of looth of an inch being easily read 

 without the aid of any vernier or maanifier. 



Farther Particulars and Prices 0/ this and other 



long range "Barometers sent on application 



to the Manufacturers— 



NEGRETTI & ZAMBRA, 



38 HOLBORN VIADUCT, E.G. 



Branches: 45 CORNHILL, and 122 REGENT 

 STREET, LONDON. 



