726 



SCIENCE 



[N. S. Vol. XLIII. No. 1116 



stance, if two equal exposures were made on a 

 plate, the second was found to give fainter images; 

 if, by means of a small prism, exposures were 

 made simultaneously with, different apertures, the 

 smaller aperture indicated a brighter magnitude 

 than the larger, when the stars were bright, and a 

 fainter magnitude when they were faint. The 

 color equation was found to vary by different 

 amounts not only for different instruments, but for 

 different magnitudes. 



Monochromatic Photography of Jupiter, Saturn- 

 and the Moon. (Illustrated by Color-photo- 

 graphs made with the Mt. Wilson 60-ineh tele- 

 scope) : Egbert Williams Wood. 

 On the Eclipses of Jupiter's Satellites: John Q. 

 Stewart. (Introduced by Professor H. N. 

 Eussell.) 

 On the Probaile Temperature of Mars: Hknrt 



NoRRis Eussell. 

 A New Catalogue of Variable Stars: Annie J. 

 Cannon. (Introduced by Professor E. C. Pick- 

 ering.) 



The first variable star was discovered in 1596, 

 and two hundred years later, when the first Cata- 

 logue was made, there were but twelve known. A 

 catalogue of 113 variable stars was published in 

 Germany in 1865. In 1888 when the first cata- 

 logue of them was made in America, the list con- 

 tained 225 stars. About this time, the Harvard 

 photographic work was established by the director, 

 E. C. Pickering. One of the first results of a 

 study of these photographs was the discovery of 

 large numbers of variable stars. They were found 

 by four methods: by arranging groups of stars in 

 sequences; by the presence of bright lines in their 

 spectra, when photographed with an objective 

 prism; by multiple exposures on the same stars 

 throughout the whole night; and by superposing 

 a glass positive and negative of the same region. 

 The globular clusters, the Magellanic clouds, and 

 the map of the sky have proved fruitful fields for 

 this investigation. So great has been the increase 

 in number that a new Catalogue now being com- 

 piled contains 4,641 stars, of which 3,397, or 

 nearly three quarters of the whole, have been 

 found at Harvard, and 1,244 elsewhere, by as- 

 tronomers in nearly all portions of the civilized 

 world. The variable stars are divided into five 

 classes, dependent upon the character of their 

 variation in light. The periods vary from two 

 hours to 698 days. Determination of the periods 

 and light curves of these stars constitute a large 

 piece of work. Much has been done at Harvard 



in this field, and many observations have been fur- 

 nished other astronomers for such determinations. 

 No more suitable place could be found for the 

 preparation of this catalogue than the Harvard 

 Observatory, for the rich library of a quarter of a 

 million stellar photographs furnishes the only com- 

 plete material in the world for the study of these 

 stars during the last twenty-five years. By ex- 

 amining the past history of a star on these photo- 

 graphs, the investigator may far more read- 

 ily find an answer to such perplexing questions 

 as to whether a star is variable or constant, what 

 is the length of the period, is the period change- 

 able, what is the color or the spectrum of the star, 

 than by waiting months or years to accumulate ad- 

 ditional observations. 



Legal and Political International Questions and 

 the Becurrence of War: Thomas Willing 

 Balch. 



saturday, april 15 



Afternoon Session — 2 o'clock 



William W. Keen, M.D., LL.D., President, in the 



Chair 

 Symposium on International Law: Its Foundation, 

 Obligation and Future: 

 Outline: Hon. John Bassbtt Moore. 

 Judicial Aspects: International Arbitration: 



Hon. Charlemagne Tower. 

 Legislative Aspects: George Grafton Wilson. 



(Introduced by Hon. John Bassett Moore.) 

 Administrative Aspects: Philip Marshall 

 Brown. (Introduced by Hon. Charlemagne 

 Tower.) 

 World Organization: Hon. David Jayne Hill. 

 On Saturday evening, April 15, at 7:30 o'clock, 

 the annual dinner was held in the North Garden of 

 the Bellevue^Stratford, at which more than one 

 hundred members and guests were present. The 

 president was particularly happy and witty in his 

 introductions of the speakers, who responded to 

 the toasts as follows: 



"The Memory of Franklin," by P*rofessor A. 

 Trowbridge. 



"Our 'Sister Societies," by Professor E. A. 

 Millikan. 



' ' Our Universities, ' ' by Professor J. M. Coulter. 

 ' ' The American Philosophical Society, ' ' by Pro- 

 fessor F. E. Schelling. 



Thus ended perhaps the most notable meeting 

 since the Franklin Celebration. 



Arthur W. Goodspebd 

 Philadelphia, 

 April 17, 1916 



