202 SCIENCE PROGRESS 



taken at the 19 14 eclipse, his value being still greater than the 

 value found for prominences. 



The study of motion in prominences is being developed, 

 and has already yielded important results. The rocket type 

 of sun-spot prominence appears to be caused by an inter- 

 mittent explosive force in sun-spots, the matter falling back 

 again on to the sun's surface. The eruptive prominences 

 indicate the presence of powerful forces which may last for 

 several hours, and which apparently neutralise gravity, for the 

 matter is not seen to descend, but fades away at a great height. 

 In Kodaikanal Obs. Bull. lv. 191 7, Mr. Evershed describes a 

 remarkable prominence which fortunately was observed both 

 at Kodaikanal and by him in Kashmir, a complete series of 

 observations being obtained. This prominence was the highest 

 ever observed, reaching a height of i8'"5, or over half a million 

 miles, before fading away. The motion was accelerated and 

 radial from the base of the prominence, the greatest velocity 

 being 457 kms. per sec. 



Observation appears to indicate that prominences, even 

 the largest, are always very tenuous. If this is so, they cannot 

 possess a temperature in the ordinary sense, but are luminous 

 on account of the absorption of solar radiation. Mr. Evershed 

 indicates as the most important problems connected with 

 prominences which await solution, the causes and nature of 

 their changes in density and luminosity, and of their differ- 

 ences in these respects, and a knowledge of their average 

 density. 



The memoir is illustrated with numerous fine reproduc- 

 tions of photographs of typical prominences. 



The following notes refer to some of the more important 

 papers recently published : 



History. — Knobel, E. B., On Frederick de Houtman's 

 Catalogue of Southern Stars, and the origin of the Southern 

 Constellations, M.N., R.A.S., 77, 414, 191 7. 



Dreyer, J. L. E., On Tycho Brahe's Catalogue of Stars, 

 Observatory 40, 229, 191 7. 



The Solar System. — Lau, H. E., Die periodischen Veran- 

 derungen auf dem Mars, I. Teil, Ast. Nach. 4878-9 ; II. Teil, 

 Ast. Nach. 4884-5; III. Teil, Ast. Nach, 4889-90, 191 7. 



