588 proceedings: philosophical society 



from 0.77 calories per minute in December to 1.55 calories in June. 

 When clouds are near the Sun, but do not obscure it, the momentary- 

 rates are increased by about 0.15 calorie per minute. The diffuse sky- 

 radiation received on a horizontal surface at noon averages about 25 

 per cent of that received on the same surface from the Sun. On a 

 clear summer day it amounts to from one-eighth to one-third of the 

 total radiation. The paper was illustrated by lantern slides. The com- 

 munication was discussed by Messrs. Bowie and Humphreys. 



Mr. F. E. FowLE then presented an illustrated paper on Atmospheric 

 transparency and Avogadro\s constant. A brief summary of this paper 

 was published in this Journal, 4: 529-530. 1914. The paper was dis- 

 cussed by Messrs. Humphreys, Bowie, and Eichelberger. 



The 744th meeting was held on October 24, 1914, at the Cosmos 

 Club, President Fischer in the chair; 22 persons present. 



Mr. W. W. CoBLENTZ presented a paper on A comparison of stellar 

 radiometers and radiometric measurements on stars. It was shown there 

 is but little difference in the radiation sensitivity of stellar thermo- 

 couples constructed of bismuth-platinum or of bismuth-bismuth + tin 

 alloy. An improved method of maintaining vacuum by means of me- 

 tallic calcium was used. Measurements were made on 112 celestial 

 bodies, including 105 stars, quantitatively on stars to the 5.3 magnitude 

 and qualitatively to the 6.7 magnitude. It was found that red stars 

 emit from 2 to 3 times as much total radiation as blue stars of the same 

 photometric magnitude. Measurements were made on the transmis- 

 sion of radiation of stars through an absorption cell of water; these 

 showed that, of the total radiation emitted, the blue stars have about 

 2 times as much radiation as the yellow stars and about 3 times as much 

 as the rec^ stars. A stellar thermocouple in comparison with a bolo- 

 meter was found more sensitive. The investigation showed that the 

 sensitivity required to do much successful work in stellar spectral en- 

 ergy curves would be 100 times that of the apparatus used, which was 

 such that when combined with a 3-foot reflecting telescope a deflection 

 of 1 mm. would have resulted when exposed to a candle 53 miles dis- 

 tant. The paper was discussed by Messrs. Swann and Wenner. 



Mr. H. L. Curtis then spoke on Insidating properties of solid dielec- 

 trics ivith special reference to surface films. A summary of this paper 

 appeared in this Journal, 4: 492, 1914. The paper was chscussed by 

 Messrs. C. A. Briggs, Burgess, Swann, and Stillman. 



The 745th meeting was held on November 7, 1914, at the Cosmos 

 Club; President Fischer in the chair; 49 persons present. 



By invitation, Mr. J. Johnston spoke on Soine effects of high pres- 

 sure. Thorough investigation of the effects producible by high pres- 

 sure will yield information of very great value in its bearing upon 

 many fundamental problems of physics and chemistry. For example, 

 it would seem that we are much more likely to ascertain precisely what 

 happens when a crystal melts by studying this process through a wide 



