84 CATALOGUE OF EXHIBITS. 



14. Still for the Purification of Water for experiments in 



conductivity. Exhibited by G. A. Hulett. Princeton 

 University. 



15. Photographs of Curves showing conductivities of various 



electrolytes and the hydrolysis of stannic chloride. 

 Exhibited by William Foster, Jr. Princeton Uni- 

 versity. 



16. Glass Positives comparing metallic and solar spectra. 



17. Glass Positives showing effect on spectra produced by in- 



creased atmospheric pressure on the arc. 



18. Glass Positives showing Zeeman effect in spectra. 



19. Glass Positives showing the displacement of spectrum 



lines by the rotation of the sun. Dopplar principle. 

 Nos. 16-19 ; taken at John Hopkins University and 

 exhibited by J. S. Ames. 



20. Mechanical Illustration of Kirchhoff's Principle. 



Exhibited by W. Hal lock. 



21. Thompson Double Bridge, improved form of, for the 



measurement of low resistance, reading directly to 

 0.000001 ohm. Manufactured by Hartmann and 

 Braun of Frankfort. Exhibited by H. C. Parker. 



22. Reichsanstalt Standard Clark Cell. 



Exhibited by H. C. Parker. 



23. Bridge for the Comparison of Standard Ohms by the 



Carey-Foster Method. Manufactured by Queen & 

 Co. Exhibited by H. C. Parker. 



24. Wehnelt's Electrolytic Interrupter, a form of, for in- 



duction coils. Exhibited by F. L. Tufts. 



25. A Platinum Thermometer for the measurement of low 



temperatures. 



Designed and exhibited by C. C. Trowbridge. 



26. Metallic Bodies used in determining the specific heat of 



metals at low temperatures, (-f 1 5° to — i82°C.) 

 Exhibited by C. C. Trowbridge. 



