Decembeh 11, 1908] 



SCIENCE 



853 



auspices of the Carnegie Institution, from 1903 to 

 1905. The methods and precautions adopted for 

 making the photographs and for measuring and 

 reducing them were described in some detail and 

 the results exhibited for twenty-three stars. This 

 paper is to be published in the Astrophysical 

 Journal. 

 Measurement of Starlight with a Selenium 



Photometer: Joel Stebbins. 



This paper presents the results of experiments 

 on the use of selenium in stellar photometry. 

 It is well known that the crystalline form of 

 selenium decreases its electrical resistance when 

 exposed to light. The method is to cast an extra- 

 focal image of a star upon a selenium surface, 

 and note the effect by means of a galvanometer. 

 Using a 12-inch telescope, it has been possible to 

 measure first and second magnitude stars with 

 about the same accuracy that is obtained in 

 visual methods. Tests with brighter artificial 

 lights give a probable error of less than one per 

 cent, for a single measurement. 



In the course of a year the sensibility of the 

 apparatus has been increased one hundredfold, 

 and it is hoped that further improvements in the 

 elimination of disturbing factors will produce 

 extremely accurate results. , 



Spectra graphic Observations: E. B. Fbost. 



A favorable report may be made upon the re- 

 sult of re-annealing by the original maker, M. 

 Parra-Mantois, of Paris, of the three large flint 

 prisms first made for the Bruce spectrograph and 

 discarded on aceoimt of lack of homogeneity. 



The star 46 (Upsilon) Sagittarii, which has 

 been qualitatively studied by Miss Cannon at 

 Harvard, and was foimd to be a spectroscopic 

 binary by Campbell some years ago, has recently 

 been observed, and a number of plates have been 

 measured by Dr. D. V. Guthrie. He finds a range 

 of velocity from + 55 km. to — 25 1cm. The 

 bright lines are not conspicuous on our plates, 

 and can be seen with certainty only on the thir- 

 teenth plate. 



Observations of the fainter component of f Ursw 

 Majoris (Mizar) have been continued for several 

 months, the measures being made by Mr. Lee. 

 A careful study by the writer has failed to bring 

 out a regular periodicity in the radial velocity, 

 and the indications are that more than two bodies 

 are involved. 



Mention was made of certain new spectroscopic 

 binaries : 



Sagittarii (IS'Sg", — 27° 6'), of Orion type, 

 which shows a large range of velocity. 



/3 Trianguli (2" 4'", +34° 31'), Ia2, which was 

 suspected from preliminary examination here, and 

 established by measures of the same plates at 

 Columbia University by Professor S. A. Mitchell. 



55 Ursw Majoris (ll'-M", +38° 44'), Ia2, 

 found by Mr. Lee; range thus far: 40 km. 



I AndromedcB (23" 33", +42° 43'), of Orion 

 type, found by Mr. Barrett, probably of rather 

 long period. 

 The Figure of the Sun and Possible Variations 



in its Size and Shape: Chas. Lane Poor. 



The first part of this paper contains a rgsumS 

 of the more important investigations of von 

 Lindenau, Secchi, Auwers, Newcomb and Am- 

 bronn. In practically every ease the original 

 reductions showed periodic variations in the diam- 

 eter of the Sim. Auwers discussed an immense 

 mass of meridian circle and heliometer observa- 

 tions and reached the conclusion that the sim is 

 sensibly a sphere and that the observed variations 

 are due to personal and instrumental causes. 

 This conclusion, however, was reached only by 

 attributing variable personal equations to the 

 different observers. 



The second part contains a retabulation and 

 rediscussion of the heliometer observations used 

 by Auwers and of those made by Schur and 

 Ambronn. It is here shown that these observa- 

 tions indicate a periodic variation in the shape 

 of the sun, the period being the same as that of 

 the sun-spot cycle. The observations of Schur 

 and Ambronn were also investigated for short 

 period vibrations by means of the method of 

 " Time Correlation " as developed by Newcomb. 

 These observations indicate a semi-permanent fluc- 

 tuation in the shape of the sun having a period 

 of about 28 days. 

 Results of Photometric Iiwestigations : E. H. 



Seabes. 



Light-curves were shown for RS Draconis, 

 VY Cygni, RV Tauri, SU Andromed<E, RS Bootis, 

 52.1907 Ophiuchi and 43.1907 Draconis. All are 

 interesting and unusual types of variation. The 

 last four are of the so-called Antalgol type with 

 periods ranging from ten to sixteen hours. 



In addition, there was presented a simple and 

 general method of determining the circular ele- 

 ments and relative dimensions of a binary system 

 on the basis of an observed light variation of the 

 Algol type. The arrangement of the method is 

 such that the light-curve corresponding to the 

 first approximation for the elements and dimen- 

 sions must be tangent to the observed curve at 

 two points. Differential formulte can then be 



