216 CARNEGIE INSTITUTION OF WASHINGTON. 



ures of the parallax of the central stars of planetaries, indicatmg their 

 faint absolute magnitudes and showing their distances to be of the 

 same order as those of Novse, are cases in point (p. 237). Including 

 five of these objects, 22 new trigonometrical parallaxes have been 

 completed this year, making 122 in all. A few spiral nebulae are in- 

 cluded in the list, though not with the expectation of finding measur- 

 able parallaxes. 



The magnitudes of all stars recorded by the 60-inch reflector in ex- 

 posures of 15 minutes on Kapteyn's Selected Areas Nos. 1 to 139 have 

 been completely measured and reduced under the direction of Mr. 

 Scares. The results are being prepared for publication in connection 

 with Professor Kapteyn's magnitude determinations for the same areas 

 on plates of longer exposure, the first large installment of which has 

 been received from Groningen (p. 239). 



The continuation of Mr. Shapley's investigations of star-clusters 

 has added further arguments in support of his view that the galactic 

 system is very much larger than was formerly supposed from consid- 

 erations based on the brighter stars. If his conclusions are correct, 

 the brightest stars in globular clusters must be giants; if the other 

 view is sound, they must be dwarfs. 



The question, on which evidence had already been secured from a 

 study of the spectra of certain of the brighter stars, photographed 

 by Mr. Pease with a slit spectrograph, has been further tested by 

 the aid of the device already mentioned — a large prism, of small 

 angle, mounted near the 134-foot focus of the Hooker telescope. The 

 continuous spectra of the stars in clusters, from X3800 to X7500, are 

 thus photographed on Ilford panchromatic plates, on which well- 

 known giants and dwarfs, of determined spectral type, are also pho- 

 tographed for comparison. The distribution of light in the spectra 

 of the brightest cluster-stars corresponds with that of known giants 

 of the same spectral type as the cluster-stars, and is characteristic- 

 ally different from that of known dwarfs (p. 242). 



The fainter stars in clusters are hardly less interesting, and the use 

 of an intensifying lens with the Hooker telescope has enabled Mr. 

 Shapley to photograph much fainter objects than could be reached 

 formerly. He has also continued his studies of globular and open clus- 

 ters, analyzed the characteristics of 1,152 giant stars in 9 clusters, and 

 determined the total intrinsic luminosities of 40 globular clusters, which 

 he finds, on the average, to give 275,000 times as much light as the sun. 



Mr. Shapley's investigation of the faint globular cluster M 72 has 

 revealed the presence of many variables, 26 of which have been studied, 

 giving the light-curves and periods characteristic of Cepheids of the 

 cluster type, and indicating that the distance of this very remote cluster 

 is 83,000 light years. Assuming the validity of Eddington's theory of 

 the radiative equilibrium of a giant star, he has derived theoretically a 



