850 



SCIENCE. 



[N. S. Vol. IX. No. 233. 



SECTION OF ASTRONOMY AND PHYSICS, OF THE 



NEW YORK ACADEMY OF SCIENCES, 



MAY 1, 1S99. 



The regular meeting of the Astronomy and 

 Physics Section was held at 12 West 31st 

 Street, New York, on May 1, 1899, Professor 

 Pupin, the Chairman of the Section, presiding. 



The first paper, describing experiments by 

 Professor Pupin and Mr. F. Townsend, on the 

 magnetization of iron with alternating currents, 

 was read by Mr. Townsend. The" paper was 

 only a preliminary account, as the experiments 

 are still in progress. The current wave in a 

 transformer with open secondary circuit is a 

 comjjlex harmonic vibration, and the particular 

 object of this research is to determine the am. 

 plitudes and phase relations of the components 

 of the fundamental vibration. 



The component due to eddy currents is de- 

 termined from the curves of electromotive 

 force and current, together with the static 

 hysteresis loop for the given magnetization, by 

 a graphical method. The eddy current com- 

 ponent is found to lag behind the electromotive 

 force. Also, the dynamic hysteresis loop is 

 found to have a rounded point, as distinguished 

 from the sharp point characteristic of the static 

 loop. 



The phase of the fundamental of the total 

 current wave is found by means of a specially 

 constructed phase meter. Its amplitude is de- 

 termined from the electromotive force and total 

 watts. 



The remaining component to be determined 

 is that due to hysteresis and induction reaction. 

 This and the eddy current component form two 

 sides of a parallelogram of which the fundamen- 

 tal of the total current wave is the diagonal. If 

 the last two are determined in amplitude and 

 phase the fundamental of the distorted wave of 

 magnetizing current can readily be found. 



The ultimate object of the investigation is to 

 formulate the laws which govern the reactions 

 accompanying the magnetization of iron by 

 alternating currents. 



The second paper was by Mr. C. C. Trow- 

 bridge on phosphorescent substances at liquid- 

 air temperatures. Calcium sulphide, made 

 phosphorescent by exposure to sunlight at ordi- 

 nary temperatures, was made non-luminous by 



immersion in liquid air. Then, when allowed 

 to heat up gradually to normal temperature, 

 the phosphorescence again became visible at 

 about — 100° to — 75° C. The same material, 

 if exposed to sunlight while immersed in liquid 

 air, phosphoresced faintly while still immersed. 

 When exposed to the electric arc it phospho- 

 resced strongly. In both of these cases the 

 phosphorescence became brighter when the 

 temperature was raised. From these results, 

 and what was previously known, it was con- 

 eluded that when a phosphorescent substance 

 like calcium sulphide is excited by light the 

 phosphorescent energy will be given up at the 

 temperature of excitation even when as low as 

 — 190° C. But if it is cooled below the tem- 

 perature of excitation the phosphorescent dis- 

 charge is arrested, and remains so until the 

 temperature is raised again until it is within at 

 least 100° of the temperature of excitation. 



It was found that calcium tungstate, which 

 gives a whitish fluorescence when exposed to 

 Rontgen rays, gave a green phosphorescence 

 when exposed to light while immersed in 

 liquid air. 



Wm. S. Day, 

 Secretary. 



DISSCUaiON AND CORRESPONDENCE. 



CEREBRAL LIGHT : FURTHER OBSERVATIONS. 



In Science, 1897 N. S. VI. 188, I published a 

 set of observations to prove that what is at 

 present considered to be retinal light arising 

 from chemical changes in the retina is really 

 not derived from the retina but from the brain. 

 The observations were essentially : 1. That 

 there was only one field of light instead of two, 

 and that this field showed no signs of binocular 

 union, binocular strife or stereoscopic union. 

 2. That the figures in the light do not change 

 as the eye moves, but follow the movement 

 later. 3. That the figures do not show move- 

 ment when the eye is displaced by pressure 

 with the fingers. A recent German reviewer, 

 while admitting the possibility that the light is 

 cerebral and not retinal, refuses to accept my 

 observations as sufficient proof. 



Last night I was able to perform what seems 

 to be a crucial exi^eriment ; I record its results 



