fjl In 1857 Negretti and Zambra first constructed 

 the Deep-sea Thermometer upon Six's principle 

 (now termed the " Miller" type), which was proved 

 capable of resisting great pressure. 

 {If In 1878 they produced and patented the 

 "Reversing" pattern, which may be supplied 

 in " Magnaghi " or " Scottish " frames. 

 {Jj Since that time many improvements have been 

 * embodied, and their most recent Deep-sea 

 Thermometers provide a very open range, enabling 

 much finer readings to be observed, are fitted with 

 an auxiliary thermometer, have the capacity 

 determined, etc. 



{11 A descriptive pamphlet, and price lists 

 -" of any other instruments, will be gladly 

 forwarded post free on request. 



NEGRETTI & ZAMBRA 



Makers of Oceanographical, Meteorological, 

 Optical, Nautical, and Surveying Instruments. 



Holborn Viaduct, London, E.G. 

 Branches: 45 Cornhill, E.G.; 122, Regent St., W. 



LEITZ 

 New and Improved Microscopes 



SUITABLE FOR EVERY 

 REQUIREMENT 



in a variety of models, possessing many advantages 

 over the older type, and embodying several im- 

 portant features not to be found in any others. 



LEITZ ENGLISH MODEL MICRO- 

 SCOPES, combining the most important features 

 of the English and Continental Stands. 



Portable Microscopes, Binocular and Mon- 

 ocular Dissecting Microscopes, Aplanatic 

 Pocket Lenses. 



Microtomes, Photo-micrographic Apparatus, 

 Projection Lanterns, Prism Field and Opera 

 Glasses, etc. 



Descriptive Price Lists of any or all of above post free. 



E. LEITZ, 18 Bloomsbury Sq., London, W.C. 



