SCIENCE 



FRroAT, June 4, 1915 



CONTENTS 



The Electrical Photometry of Stars: Professor 

 Joel Stebbins 809 



Mr. Edison's Service for Science: President 

 ElCHARD C. Maclaurin 813 



The Proceedings of the National Academy as 

 a Medium of Publication: Dr. George El- 

 LERT Hale 815 



The Seattle Meeting of the American Chem- 

 ical Society: De. Chas. L. Parsons 817 



Scientific Notes and News 818 



University and Educational News 822 



Discussion and Corres'pondence : — • 



Bird Collecting and Ornithologv : Dr. Wil- 

 LABD Gr. "Van Name. Fundamental Equa- 

 tions of Mechanics : T. L. Porter and B. 0. 

 GowBT. Another State Parle Needed : E. C. 

 Benedict 823 



Scientific BooTcs: — 



Stevens's. Theory of Measurements: Pro- 

 fessor A. DE Forest Palmer. Child on 

 Electric Arcs: Professor E. G. Hudson . . . 828 



Scientific Journals and Articles 829 



Scientific Sesults of the Terra Nova Expedi- 

 tion : Dr. Edward W. Berry 830 



Special Articles: — 



A Botanical Index of Cretaceous and Ter- 

 tiary Climates: I. W. Bailey and E. W. 

 iSiNNOTT. The Brown Grape Aphid: A. 0. 

 Bakee and "W. E. Turner. The Relation 

 of Mitochondria to Granules of the Vital 

 Azo Dyes: Katherine J. Scott 831 



The American Philosophical Society: Pro- 

 fessor Horace Clark Eichards 835 



The American Physical Society: Professor 

 A. D. Cole 841 



Tlie Entomological Society of America: Pro- 

 fessor Alex. D. MacGillivray 842 



The Indiana Academy of Soien<;e: De. A. J. 

 Bigney 843 



MSS. Intended for publication and books, etc., intended for 

 reylew should be sent to Professor J , MoKeenrattell.Garr'soo- 

 On-HudsOD, N. Y. 



THE ELECTMICAL PHOTOMETRY OF STABS^ 

 In measures of the light of stars there 

 are some advantages and some drawbacks 

 as compared with photometric work in the 

 laboratory. First of all, we are not con- 

 cerned with absolute measures of intensity, 

 but what we want to know is how the light 

 of a heavenly body varies. If the light is 

 constant, there is not much to be learned, 

 but if it changes, we may infer a great deal 

 from the law of variation. In laboratory 

 and commercial photometry, it is customary 

 to measure what may be called the visual 

 brightness of a source of light, but with the 

 stars it is immaterial for many purposes 

 whether we study the changes of the red, or 

 the blue, or any other part of the spectrum, 

 though in fact any complete stellar photom- 

 etry should include measures in all regions, 

 infra-red, visible and ultra-violet. 



The chief disadvantage in stellar photom- 

 etry is that the stars are so faint that it is 

 usually not feasible to expand their images 

 out into surfaces, and most forms of stellar 

 photometer depend upon comparisons of 

 two point images by the eye. Although the 

 eye is a wonderful instrument, especially 

 in the range of intensity over which it may 

 be used, the limit of accuracy attained by 

 looking first at one light and then at another 

 is much the same as though instead of using 

 a balance we should weigh objects by lift- 

 ing them in our hands. It is safe to say 

 that no observer has ever been able to get 

 visual results accurate to 1 per cent., and 

 in the best measures there are occasional 

 errors of 10 per cent., 20 per cent, and 

 even more. It was hoped that the introduc- 

 1 Read at the meeting of the National Academy 

 of Sciences, April. 20, 1915. 



