SCIENCE-ADVERTISEMENTS 



NEW EDITION OF THORPE'S DICTIONARY OF CHEMISTRY 

 Now Complete In Five Volumes 



A DICTIONARY OF APPLIED CHEMISTRY 



By Sir Edward Thorpe, C.B., LL.D., F.R.S., Emeritus-Professor of Chemistry, Imperial College of 

 Science and Teclinology, South Kensington, London, etc. Assisted by eminent contributors. 

 Revised and Enlarged Edition in 5 Vols. With Illustrations. Eoyal 8vo. Vol. I. A — Che; Vol. 

 II. Chi— Go; Vol. III. Gr— Oils; Vol. IV. Oilstone— Soda Nitre; Vol. V. Sodium— Z. $67.50 

 net. Separately, each volume, $13.50 net (Postage Extra). 



" The revision and publication of these volumes has been a great undertaking and it is gratifying 

 to iind that both the editor's work and the mechanical production have been accomplished with such 

 promptness and success. In its present revised form, it is doubtless the most comprehensive and com- 

 plete book of reference now in existence covering the broad field of applied chemistry." 



— 31. 0. Whitaker in Journal of Industrial and Engineering Chemistry. 



" The last volume fully maintains the standard of the earlier parts of the work, most of the articles 

 written by acknowledged authorities being models of concise and up-to-date knowledge." — Athenaeum. 



" If every manufacturer is wise enough to add this work to his library he will have available a 

 mine of information that will constantly save him fruitless inquiry and laborious research. . . . 

 Worth a whole library of ordinary chemical literature." —Drugs, Oils, and Faints. 



CATALOGUE OF SCIENCE 



Longmans, Green, & Co. 



BOOKS ON REQUEST 



4th Ave. & 30th St., N. Y. 



Leitz' Improved Petrographic Microscope 



after specifications of Dr. Albert Johannsen, of Chicago 

 The Johannsen Stand differs in many directions from all existing models 

 Enlarged diameter of Microscope tube. 



I The field of view is twice as large. 2 Polarization appliances can be accommo- 

 dated more conveniently. 



Iris diaphragm above Bertrand lens, the latter supplied with centering 



screws. 



Tube provided with scale and vernier. 



The respective position of the Bertrand lens can be determined with the 



aid of this scale. 



New Objective clutch changer supplied with individual center- 

 ing heads for the objectives. 



Every objective is furnished with separate centering head and is centered 

 individually with watch key in order to remain permanently centered. 



New Condensers with different types of iris diaphragms. 



One of the diaphragms serves the purpose to exclude a certain grain from 

 the object under observation in order to view interference figures of same. 



Johannsen Combination Wedge 



offers many advantages. 



Write for literature 0—69 



u. s. 



BRANCH 



30 E. 18th Street 

 NEW YORK 



Factory: WETZLAR, GERMANY 



