SCIENCE— ADVERTISEMENTS 



In every laboratory where electricity is used, there is need for 



variable resistances — and to meet such requirements 



we offer a well tried series of 



"JAGABF SLIDING CONTACT 



TUBE RHEOSTATS 



Hundreds of them have been sold during the past three years, to various Govern- 

 ment Departments, Universities, Colleges, Technical Schools, Industrial Com- 

 panies, etc. — and have "made good" under every-day service conditions. 



WRITE FOR ILLUSTRATED DESCRIPTIVE BULLETIN 937 



JAMES G. BIDDLE 



1211-13 ARCH STREET, PHILADELPHIA 



