November 16, 1906.] 



SCIENCE. 



611 



to cause a spark to pass between a ball and 

 plate were made, with kerosene, olive oil, 

 paraffin oil and a transformer oil as the 

 intervening dielectrics. 



Distances of separation vary from .003 

 to .118 mm. and were measured in terms 

 of wave-lengths of sodium light. 



A plane surface was attached to the 

 movable carriage of an interferometer. 

 This was brought in contact with a ball 

 mounted on the interferometer base. These 

 were separated and the fringes crossing the 

 interferometer field noted. From this data 

 distances of separation of the surfaces were 

 computed. 



P.D.'s were obtained from an A.C. trans- 

 former and were measured with a "Weston 

 voltmeter. 



The data secured are compared with sim- 

 ilar measurements made by the author 

 when air was used as a dielectric. 



Spark potential-distance curves for the 

 various oils used give curves similar in 

 form to those for air. 



These experiments on the limited num- 

 ber of oils used indicate: 



1. A higher potential gradient for small 

 than for large distances. 



2. That for small distances air is a better 

 insulator than a liquid dielectric, 



3. That the potential at which the bend 

 in the potential-distance curve occurs is the 

 same for air and the liquids operated upon. 



The Dispersion of Silver Chloride: E, F. 

 Nichols and W. S. Day, Columbia Uni- 

 versity, 



Properties of Electric Charges on Moving 

 Conductors: E. F. Nichols, Columbia 

 University. 



The Separation of Electric Charges in a 

 Metal iy Centrifugal Acceleration: E, 

 P, Nichols, Columbia University, 



Comparative Observations on the Evolution 

 of Gas from the Cathode with the Glow 

 Current in Helium and Argon: Clar- 

 ence A. Skinner, University of Ne- 

 braska. 



The Effect of Absorbed Hydrogen on the 



Photoelectric Current: "W, F. Holman, 



University of Nebraska, 



Light from a spark are between iron 

 terminals in hydrogen was directed through 

 a quartz optical system on to a zinc disk, 

 serving as cathode— a disk of aluminum 

 opposite serving as anode — the electrodes 

 being in a highly evacuated chamber. 

 Under these conditions the rate of leak of 

 negative electricity from the zinc was rep- 

 resented by 32 scale divisions of the meas- 

 uring instrument. 



The zinc was then partially relieved of 

 its supply of hydrogen by use as cathode 

 with the glow discharge in hydrogen, after 

 which it was again tested as before for its 

 photoelectric current, which was found to 

 be now represented by only about 22 scale 

 divisions. This test was followed by using 

 the zinc as anode with the glow discharge 

 in hydrogen, the object of which process 

 was to store up in it a new supply of 

 hydrogen. A test of the photoelectric cur- 

 rent as before showed that it had returned 

 to its first value, giving, namely, a deflec- 

 tion of about 32 scale divisions. 



The Production of Ozone by Becquerel 

 Bays: Harry S. Hower, Case School of 

 Applied Science. 



The Production of Ozone by the Photo- 

 electric Current in Oxygen: Harry S, 

 Hower, Case School of Applied Science. 



Fluorescence Absorption in Besorufin: 

 Frances Wicke, Cornell University. 



Further Experiments on the Phosphores- 

 cence of Sidot Blende: E, L. Nichols 

 and Ernest Merritt, Cornell University, 



