RECENT ADVANCES IN SCIENCE 203 



Three lengthy papers dealing with observations, past and 

 present, of the surface-markings of Mars. 



Nicholson, S. B., The Ninth Satellite of Jupiter, Proc. 

 Nat. Acad. Set., 3, 417, 191 7. The orbit is given, and from 

 the magnitude and probable albedo the diameter is found to 

 be about 15 miles. 



Struve, G., Neue Bestimmung des Saturnsaquators und 

 der Bahnlageelemente der inneren Saturnstrabanten, Ast. Nach. 

 4880, 191 7. Observations by H. Struve at Poulkowa and more 

 recent observations at Washington and Babelsberg are com- 

 bined to deduce a definite position for Saturn's equator. The 

 result agrees well with that obtained by H. Struve. 



Picart, L., Sur l'Application de la Methode de Lagrange- 

 Cauchy au Calcul d'une Orbite definitive, Bull. Astron. 34, 

 I 35> 1917- To determine an orbit from three observations at 

 widely separated epochs the methods of Lagrange and Gauss 

 are not suitable. The only method is that of Lagrange-Cauchy ; 

 this method has been adapted for calculation by Picart and 

 the process of computation is illustrated. 



Slipher, V. M., Spectral Evidence of a Persistent Aurora, 

 Lowell Obs. Bulletin, j6, 1916. By spectroscopic evidence a 

 permanent illumination of the night-sky by the aurora is 

 proved. 



Hough, S. S., A Determination of the Constant of Aberra- 

 tion, M.N., R.A.S. 77, 484, 191 7- The value is deduced 

 from observations made with the Cape reversible transit-circle, 

 using Gill's very stable meridian marks. A programme for 

 obtaining the constant with greater weight is sketched out. 



Orbits of Binary Systems. — Russell, H. N., The Orbit of 

 Equulei, Ast. Journ., 710, 191 7. The orbit of Krueger 60, 

 Ast. Journ. 711, 191 7. 



Comstock, G. C, The orbit of £Herculis (2 2084), Ast. Journ. 

 712, 1917. 



Young, R. K., The orbit of the spectroscopic binary, 

 2 Sagittae, Journ. R.A.S.C. 11, 127, 191 7. 



McDiamid, R. J., The Eclipsing Variable Star SS Camelo- 

 pardalis, Astroph. Journ. 45, 50, 191 7. 



The first two are of importance because the stars have 

 reached positions in their orbits in which they are in rapid 

 relative rotation, and the measures of the next few years should 

 give very accurate orbits. The third is of interest because 



