256 



SCIENCE 



[N. S. Vol. XXVIII. No. 712 



A Comparative Investigation of Dispersion and 



Electric Double Refraction in Liquids: H. E. 



McCoMB, University of Nebraska. (Presented 



by Professor C. A. Skinner.) 



Tliis study showed in general that the change 

 in refractive index follows the same law as that 

 of the constant of electric double refraction. Six 

 liquids were studied. Five of them showed this 

 agreement, but one (di-methyl-aniline) showed no 

 definite relation between the two constants. 

 Electromagnetic Mass and Energy: Daniel F. 



CoMSTocK, Massachusetts Institute of Tech- 

 nology. (Read by title.) 

 Effects of Absorbed Hydrogen and of Other Gases 



on the Photoelectric Activity of Metals: V. L. 



Cheislee, University of Nebraslca. (Presented 



by Professor 0. A. Skinner.) 



Following the method used by Holman {Phys. 

 Rev., August, 1907) the effect upon its photo- 

 electric activity of using a metal as cathode and 

 as anode in a giow current, has been investigated. 

 The effect of surroimding it by different gases has 

 also been tested. 



Using fourteen different metals, they showed, 

 without exception, a decreased photo-electric cur- 

 rent by continued use as a cathode surrounded 

 by hydrogen. On the contrary, when used for a 

 moment as an anode surroimded by the same gas 

 they showed a marked increase in activity. With 

 some metals the photo-electric current was thirty 

 times as great after using as anode as after use 

 as cathode. This effect was obtained with con- 

 ducting hydrogen; exposure to non-conducting 

 hydrogen increases the activity, but much less 

 rapidly. 



The activity of the metals practically vanished 

 after extended use in either heliiun or oxygen, 

 nor could any trace of recovery be obtained by 

 use as anode in the same gases. In nitrogen use 

 as cathode did not wholly destroy the activity; 

 with silver alone an increase was obtained by 

 use as anode, slight but definite. Carbon was 

 like silver in this respect. 



When the activity had been reduced to a van- 

 ishing quantity by use in other gases, it was 

 readily regained by introducing an atmosphere 

 of hydrogen. A gradual disappearance of hydro- 

 gen accompanied this increase in activity. After 

 use as cathode in hydrogen, the metal became 

 negatively charged; after use as an anode it was 

 positively charged. Tliese results are readily ex- 

 plained if hydrogen on being absorbed or given 

 off by the metal, carries with it a charge of nega- 

 tive electricity. Whether immediately or indi- 



rectly, hydrogen appears to be the prime agent 



in rendering metals photo-active. 



A 'Mew Method for Determining the Difference 



of Potential between a Metal and a Solution of 



One of its Solids: A. W. Ewell, Worcester 



Polytechnic Institute. 



The experiments of Ayrton and Perry on this 

 subject were repeated with some modifications. 

 A glass vessel was covered with tinfoil which 

 was connected to the needle of a Dolezaiek elec- 

 trometer. Its terminals were connected to those 

 of a 40-cell battery, earthed at the center. A 

 metal electrode placed in a solution of one of its 

 salts was also earthed. One volt gave a deflec- 

 tion of 8 cm. Copper in copper sulphate solution, 

 zinc in zinc sulphate and mercury in potassium 

 chloride were used in the measurements. 

 The Isothermal Layer of the Atmosphere: W. J. 



Humphreys, Mt. Weather Meteorological Ob- 

 servatory. 



The temperature of the atmosphere decreases 

 more or less \iniformly witli increase in elevation 

 above the surface of the earth until an elevation 

 of from 30,000 to 60,000 feet is reached, where 

 the temperature is — ■ 50° to — 60° C. From 

 this elevation up as far as balloons have gone 

 the temperature remains practically constant. 

 This is explained as the result of radiation, 

 mainly from the moisture in the air, which will 

 have an effective radiating surface of great extent 

 in comparison with elevations reached by balloons. 

 Tlie means of locating this surface was considered. 

 The relative proportion of the different constitu- 

 ents of the air is different at different elevations, 

 the proportion of water vapor being relatively 

 great in tlie lower layers. Calculation shows the 

 temperature of this " effective radiating surface " 

 to be about — 33° C. (The calculations were 

 carried through in detail before the joint session.) 

 Coefficients of Expansion at Low Temperatures: 



H. G. Dorset, Cornell University. 



Curves were drawn with temperature and ex- 

 pansion as coordinates. Temperatures used 

 ranged from 113° C. (absol.) to 213°, and were 

 secured by the use of liquid air. Selenium and 

 hard rubber gave nearly a straight line, while 

 zinc and gold gave very irregular curves. A 

 second sample of gold of greater purity (obtained 

 from the U. S. mint) gave a straight line. Fiber 

 cut in three different directions with respect to 

 the direction of its grain, was also used. 



The full paper is published in the July number 

 of the Physical Review. A. D. Cole, 



Secretary Section B. 



