February 9, 1917] 



SCIENCE 



147 



very small; amounting, indeed, more often than 

 not to but a single imit of the last tabulated deci- 

 mal place, unless the nimiber of tabular quantities 

 which have been combined exceeds twenty. Plas- 

 kett showed very interesting views of the con- 

 struction of the great 72-ineh telescope, and of the 

 observatory placed on Saanieh Hill, Vancouver Is- 

 land. The work is now practically completed ex- 

 cept for the installation of the great mirror. 



In connection with the photographic work for 

 which such great telescopes are mainly used, F. 

 E. Boss's paper, showing the superiority of some 

 kinds of developer — notably "caustic hydro- 

 chinon ' ' — in securing sharp star images, and 

 King's which showed that, when an exposed plate 

 is kept for months before development, the strong- 

 est images on it grow more intense, while the 

 weakest ones fade, are of importance. The discus- 

 sion of Flint's paper on systematic errors in the 

 determination of stellar parallax brought out an 

 apparently general confidence in the reliability of 

 the modern photographic determinations. In other 

 fields, Urie described records showing that the gov- 

 ernment wireless time signals sent out from the 

 Great Lakes station are, very consistently, about 

 one twelfth of a second later than those sent from 

 Arlington — this "lag" representing the time 

 which the signals from Washington take to reach 

 the more distant station over the telegraph lines. 

 Eussell computed that the minimum radiation vis- 

 ible to the eye carries energy at the rate of but one 

 erg in forty years. 



There were relatively few papers dealing with 

 bodies in the solar system. Bauer summarized the 

 latest results of the ocean magnetic work of the 

 Carnegie Institution; Slocum showed a fine series 

 of photographs illustrating the librations of the 

 moon; Father Rigge discussed the eclipse of De- 

 cember 13, 1917, which will be centrally annular al- 

 most exactly at the South Pole; Very described the 

 complications which the absorption of the earth's 

 atmosphere introduces into the determination of 

 the temperature of the moon; Arctowski gave the 

 results of recent work on sun-spots, and brought 

 out the remarkable fact that at Batavia, Java, the 

 weather tends distinctly to be unusually rainy on 

 days of magnetic storms — which, with other facts, 

 falls in well with the belief that the magnetic dis- 

 turbances are caused by the impact of electrically 

 charged corpuscles on the earth's atmosphere; and 

 W. E. Grlanville described and discussed his ob- 

 servations of the zodiacal light. 



As has been usual in recent years, many com- 

 munications dealt with stellar astronomy. Benja- 



min Boss and his colleagues von Flotow and Ray- 

 mond contributed six important papers on stellar 

 distribution and drift. It was found that the 

 brighter naked-eye stars tend to congregate, not 

 only towards the galactic plane, but toward a sub- 

 sidiary plane inclined about 50° to the former; that 

 in certain regions of this belt of bright stars there 

 exist tendencies toward systematic motion of a 

 type not present elsewhere; that near the south 

 galactic pole the whiter and redder stars are, for 

 the most part, moving in different directions; that 

 the stars of large proper motion tend to move par- 

 allel to one or other of two mutually rectangular 

 planes in space; that in some cases the parallaxes 

 of these stars can be estimated with considerable 

 accuracy on the basis of these motions, and so on. 

 Two papers by Shapley and Pease dealt with star- 

 clusters, one giving evidence that the great cluster 

 in Hercules is not strictly globular, but ellipsoidal, 

 and the other announcing several important obser- 

 vations, especially that many of the very faint 

 stars in the clouds which compose the Milky "Way 

 are bluish- white (which is not the case in other 

 parts of the sky), and that it is therefore probable 

 that the distance of these star clouds is much more 

 than ten thousand light years. Scares (likewise 

 from Mount Wilson photographs) finds that the 

 number of stars per square degree in the center of 

 the MUky Way is more than twenty times as great 

 as near the galactic poles — a result in remarkable 

 and still unexplained discordance with the ratio of 

 four to one obtained at Greenwich. 



Another group of communications dealt with 

 variable and double stars. Leon Campbell exhib- 

 ited the remarkably successful cooperative work of 

 amateur observers in following the peculiar vari- 

 able SS Cygni; Kunz and Stebbins reported the 

 discovery of two new variable stars in Orion — one 

 of them. Eta Orio7iis, a bright star, with variation 

 due to eclipse. Bailey discussed the light-curves of 

 cluster variables; Dugan gave a preliminary ac- 

 count of his observations on the eclipsing system 

 U Cephei, which shows a conspicuous secondary 

 minimum; and Miss Cannon, describing the spectra 

 of this same star, reported that the bright com- 

 ponent was of Class A, and the larger but fainter 

 one which totally eclipses it of Class K — so that 

 these two stars, though separated by little more 

 than the diameter of either, are spectroscopieally as 

 unlike as Sirius and Arcturus; and Eussell pre- 

 sented orbits of the visual binaries e Equulei and 

 Krueger 60 — the latter the faintest and least mas- 

 sive star whose orbit has so far been computed. 



Three important papers on nebulte close the list. 



