SCIENCE-ADVERTISEMENTS 



Vacuum 

 Thermo- Elements 



Made by 



Siemens & Halske 



The Siemens & Halske Vacuum Thermo-Ele- 

 ments are designed for measuring very small 

 alternating currents, in conjunction with suit- 

 able pointer or reflecting Gal vanom eters. Sensi- 

 bility is very high, and results of great accuracy 

 may be obtained by their use. These instru- 

 ments have been used by Public Utilities and 

 Industrial Companies, and in University and 

 College Laboratories. Shunts with several 

 ranges and multi-way svritches may be supplied 

 if required. 

 Write for Bulletin 335, giving full particulars. 



JAMES G. BIDDLE 



Sole U. S. Agent 



1211-13 Arch Street 



PHILADELPHIA 



When in Fbiladelphia be sure to visit our Permanent 

 Exhibit of Scientific iDStruinents. 



NORTHRUP 



HIGH TEMPERATURE 



ELECTRIC FURNACE 



FURNACE AND TRANSFORMER IN POSITION FOR OPERATION 



A new type of Furnace designed by Dr. Edwin F. Nor- 

 thrup for hi8 own work in the accurate determination of 

 the resistivity of the less fusible metals and alloys in the 

 Palmer Physical Laboratory of Princeton University. See 

 " Resistivity of Copper in Temperature Range 20° C. to 

 1450° C," Journal of The Franklin Institute, January, 1914. 

 A non-vacuvun furnace for use in the many operations 

 requiring constant temperatures up to a full 1600° C, with 

 special reference to work above 1180° C, the temperature 

 at which wire and ribbon wound furnaces become useless 

 for continuous operation. The heating imit does not give 

 off any contaminating vapors nor is it injured in the least 

 by any metaUic vapors arising from the charge. The 

 Furnace will melt at least 37 metals and vaporize many 

 and may be used constantly at temperatures permitting 

 the testing of high melting point glazes and the determina- 

 tion of the melting temperature of the more easily fusible 

 refractories. Its black body temperature makes it an 

 admirable de\'ice for the caUbration of optical pyrometers. 

 Continuous heating at the melting point of palladium, 

 1549.2° C. requires an energy input of 2 K.W. and 1.6 

 K.W. will give a final temperature of 1250° C. 



Price of Furnace only with unit and accessory 



equipment $360.00 net 



Price of Special Transformer, operating on 

 either 110 or 220 volts. Other primary wind- 

 ings on application. With secondary voltage 

 regulated in six steps and with a total cap- 

 acity of 4 K.W. for continuous operation. . . $165.00 net 



Price of extra graphite Heating Units with 



' ' $ 35.00 net 



ten 



Descriptive pamphlet sent on request 



ARTHUR H.THOMAS CO. 



Importers and Dealers 



MICBOSCOPES. LABORATORY AP- 

 PARATUS AND CHEMICALS 



West Washington Square, 

 PHILADELPHIA 



