y 



SCIENCE 



New Sbbies 



Vol. XLVI. No. 1186 



Friday, September 21, 1917 



Single Copies, 15 Cts. 

 Annual Sdbsoeiption, $5.00 



Mercury Vapor Air Pump 



As designed by Dr. Kraus of Clark 

 University, to be used in connection 

 with an ordinary water pump. With 

 this pump it is possible to obtain 

 practically an absolute vacuum. The 

 glass parts are carefully made of 

 special resistant Pyrex glass, so that 

 they stand repeated heating without 

 breaking. In case of breakage, re- 

 pair is easy and comparatively cheap. 



Price complete as illustrated — $25.00 



EIMER & AMEND 



Founded 1851 



Third Ave., 18th to 19th Sts. NEW YORK CITY 



Branch Offices and Showrooms 

 2011 Jenkins Arcade, Pittsburgh, Pa. 48 Sparks Street, Ottawa, Canada 



