SCIENCE-ADVERTISEMENTS 



Siemens & Halske 



Repair Shop 



Testing, Calibrating and Repair 



of Electrical Apparatus and 



Instruments 



Building and Designing; of Special 

 Apparatus fo* Scientific Investi- 

 gation and Experiments 



New York City 90 West Street 



How 5000 Schools Save 



In Buying Scientific Apparatus 



Buying- direct from our factory saves money on 

 their laboratory supplies. One profit from makerto 

 Bchool cuts out all extra selling and traveling ex- 

 penses. Ohapco Purchase Guide No. 11 free to in- 

 structors and officials. Matchourprices with others. 

 Mention your school when writingf or the book. (7) 



Chicago Apparatus Co. 65 s. Clinton St. Chicago 



JULIEN'S POWER AND FOOT LATHES 



Use of Geologists, Mineralogists, Petrographers, Met- 

 allurgists, Mining Engineers, in SLICING and POL- 

 ISHING all hard substances, rocks, etc., and in prepa- 

 ration of MICROSCOPIC THIN SECTIONS. 



GUSTAVUS D. JULIEN 

 3 Webster Terrace NEW ROCHELLE. N. Y. 



For 3ale 



One Beoktnann freezing point apparatus and one con- 

 ductivity apparatus made by Fritz Koler, Leipzig. 

 Practically unused. 



Address Q, Science, 

 Sub-Station 84 New York, N. Y. 



Shells! Shells! 



An unusual opportunity for some institution or concholo- 

 gist. About 5,700 species and varieties; over 50,000 apeei- 

 mens. All correctly named and labeled. The result of 60 

 years' collecting. Very moderate price. Address 



J. C. ROWELL 



3415 West Street Oakland, California 



John A. Brashear Co., Ltd. 



Designers and Manufacturers 



of 



High Grade Astronomical and Physical Instruments, including 

 Befracting and Reflecting Telescopes, Spectroscopes and Spectro- 

 graphs, Spectroheliographs, Astronomical Photographic Cameras for 

 wide field photography. 



Special Objectives corrected for any part of the spectrum ; Prisms 

 of any desired form or material ; Measuring Engines with precision 

 screws for spectra or stellar photographs ; Diffraction Gratings, ruled 

 by Dr. Anderson on Rowland's Engines, of the most perfect type yet 

 produced. A fine series of gratings now ready for distribution. 



Address JOHN A. BRASHEAR CO., Ltd. 

 Pittsburgh, Pa. 



