THE CENTURY'S PROGRESS IN ASTRONOMY 



In 1880 Dr. Henry Draper, at Hastings-on-the-Hudson, 

 made the first successful photograph of a nebula. Soon 

 after, Dr. David Gill, at the Cape observatory, made fine 

 photographs of a comet, and the flecks of starlight on 

 his plates first suggested the possibilities of this method 

 in charting the heavens. 



Since then star-charting with the film has come to 

 virtually supersede the old method. A concerted effort is 

 being made by astronomers in various parts of the world 

 to make a complete chart of the heavens, and before 

 the close of our century this work will be accomplished, 

 some fifty or sixty millions of visible stars being placed 

 on record with a degree of accuracy hitherto unapproach- 

 able. Moreover, other millions of stars are brought to 

 light by the negative which are too distant or dim to be 

 visible with any telescopic powers yet attained a fact 

 which wholly discredits all previous inferences as to the 

 limits of our sidereal system. Hence, notwithstanding 

 the wonderful instrumental advances of our century, 

 knowledge of the exact form and extent of pur universe 

 seems more unattainable than it seemed a century ago. 



Yet the new instruments, while leaving so much 

 untold, have revealed some vastly important secrets of 

 cosmic structure. In particular, they have set at rest 

 the long-standing doubts as to the real structure and 

 position of the mysterious nebulae those hazy masses, 

 only two or three of them visible to the unaided eye, 

 which the telescope reveals in almost limitless abundance, 

 scattered everywhere among the stars, but grouped in 

 particular about the poles of the stellar stream or disk 

 which we call the Milky Way. 



Herschel's later view, which held that some at least 

 of the nebulae are composed of a " shining fluid," in 



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