THE YEAR'S PROGRESS IN ASTRONOMY. 



By P. PuisEUX, 



Member of the Academy of Sciences, Professor at the Sorbonrie, Astronomer at the Paris 



Observatory. 



It is an illogical peculiarity of the human minrl that while it can 

 not comprehend an mfinite material universe it readily refuses to 

 limit it. Those celestial objects which hide themselves from our 

 curiosity by their almost mconceivable distances are to the astron- 

 omer the most attractive of all. He dislikes to realize the invariable 

 appearance of the nebulae, or that he can not measure their distances 

 with any approach of accuracy. Because he can find no better mode 

 of inquiry he improvises one based upon a reasonable evolutionary 

 theoiy. These impalpable phantoms he puts to the tests of his 

 laws of mechanics, of physics, to the reactions of chemistry, a legiti- 

 mate procedure, since it suggests consequences the verification of 

 which he may attempt. 



The spiral nebulas, with theu' sliarply defined structure and a 

 spectrum which is a weakened replica not too much altered of the 

 sun, takes us mto a region relatively well loiown. But when we 

 consider the gaseous neliula?, those pale, undefined flakes so constituted 

 that they have defied the power of time, how can we establish any 

 connection between them and our daily experiences? Theii* spec- 

 trum brings us little help. It sliows in the most favorable circum- 

 stances four bright enigmatic Imes with a few others which can be 

 identified as due to hydrogen or helium. 



We can not borrow any of the substance of the nebulas for analysis 

 in our laboratory. To look upon each unknown line as an indication 

 of a new element would be easy but futile. It might be useful, on 

 the other liand, to invent some molecular structure for some one 

 single element (wliich we will call nebulium) capable of producing all 

 the lines of unknown origin. That is just what J. W. Nicholson ^ has 

 done, who applied the theory of Johnstone Stoney and Ritz regarding 



' Translated by permission from Revue g^ndrale des Sciences pures et appliqu6es, Paris, June 30, 1912, 

 pp. 474-478. 

 » Session of the Royal Astronomical Society, Nov. 10, 1911. 



135 



