SCIENCE-ADVERTISEMENTS 



Weiss Electro-Magnet 



Made by Societe Genevoise 



These electromagnetB are made in 

 four different sizes to meet all labora- 

 tory requirements. 



The coils are water cooled and as 

 shown in the illustration are 

 mounted on the pole tips concentrat- 

 ing the magnetic field at that point. 

 The pole pieces may be separated by 

 a micrometer screw and the distance 

 between them read to .1 of a milli- 

 meter. 



Five different shaped pole pieces 

 may be used. The magnet is also 

 adapted for polarization and other 

 attachments. 



Duty free prices are very attrac- 

 tive. 



Write for special descriptive 

 Circular 



JAMES G. BIDDLE 



1211-13 ARCH ST. Special Representative PHILADELPHIA 



When in Philadelphia be Bure to Tisit our Permanent Exhibit of Scientific Apparatus. 



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GOODE'S BASE MAPS 



For classes in geography, geology, eco- 

 nomics, history, etc. 18 subjects. Two 

 sizes: 8xl0^in.,lc; 15x10^ in., 3c; pos- 

 tage extra. Perforated for notebook ; suit- 

 able for ink or pencil. Samples on request. 



The University of Chicago Press 

 Qiicago, Illinois 



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# OUR 1913 CATALOG 



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