SCIENCE— ADVERTISEMENTS 



Development and Improvement of Scientific Instruments and Equipment go hand in hand 

 with the development of science, and their progress is mutually beneficial 



UNIVERSAL 

 MOTOR 

 ROTATOR 



Among the many new instruments developed by W. M. Welch Scientific Company 

 may be mentioned the following: 



TJWIVERSAL MOTOR ROTATOR for Direct Current 

 or Alternating Current. Continuous speed chang- 

 ing. Produces rotation in vertical oi horizontal 

 direction. With speed counter and 6 ft. of cord. 

 Cat. No. 905. 



MODEL OF THE ATOM. Design suggested by Prof. 

 R. R. Ramsay, Indiana University. Shows stable 

 arrangement of rotating bodies similar to atoms or 

 solar system. Illustrates radio-acti^nty. Suitable 

 for projection. Cat. No. 610. 



DEMONSTRATION ORGAN PIPE. Design sug- 

 gested by Prof. Lunn, University of Chicago. 

 Shows the effect of mouth piece upon fundamental. 

 Enables holding fundamental regardless of way of 

 blowing. Shows the finer features of the organ 

 pipe design. Cat. No. 3268. 



SOURCE OF LIGHT FOR OPTICAL DISC. ParaUel 



rays for use with the Optical Disc. Avoids setting 

 up an arc. Attaches to 110 volt circuit either A.C. 

 or D.C. Cat. No. 3680. 



CHOKE COIL shows impedance factor and that Ohm's 

 law does not hold with Alternating Current. May 

 be used either as a demonstration piece or as a 

 student experiment piece. Light glows more 

 dimly when iron core is inserted in solenoid. Cat 

 No. 2610. 



AIR BRAKE MODEL. Triple valve air brake as used 

 on railway cars, with safety device in which reserve 

 supply tjf air releases brake. Cat. No. 1560. 



Full Information regarding these developments, and others will be sent upon request. 

 Ask to be put on our mailing list to receive the first notices of the new Welch Specialties. 



cA Sign of ^ality ^^^f^%€]^ ^ ^^rk of Service 



W. M. WELCH SCIENTIFIC COMPANY 



Manufacturers, Importers and Exporters of 

 Scientific Apparatus and School Supplies 



1516 Orleans Street CHICAGO, ILL- 



