24 CARNEGIE INSTITUTION 



is now coming into view as the problem of the time, surpassing in 

 the universality of its interest and in the grandeur of its scope all 

 the physical inquiries which engage the attention of scientific men. 



This problem should not be regarded, however, as synonymous 

 with the whole range of sidereal astronomy. In the sense in which 

 the term sidereal problem is employed here it would include those 

 classes of research the chief interest of which centers in their bear- 

 ing upon the description of the stellar system as a unit. There is 

 another large range of extremely interesting investigations in the 

 stellar field, in relation to which the chief interest centers in the 

 natural history of individual objects. Even these may turn out to 

 have their bearings upon the sidereal problem as a unit, but the 

 connection is not so apparent. However much one class of re- 

 searches may blend into another, the distinction here made may be 

 found a useful one in the effort to give unity of design to the aim 

 of the proposed Southern Observatory. 



To unravel the problem of the solar system was the task which 

 was first seriously proposed to astouomers three hundred years ago. 

 Galileo, Kepler, Newton, and a long line of distinguished successors 

 have successfully grappled with the intricate questions involved in 

 that problem. Now the aspirations of astronomers are reaching 

 beyond the boundaries of the solar system into stellar space. The 

 stellar problem confronts us as the serious occupation of the present 

 and the future, and it is illimitable in extent. 



Nkkd of Mork Astronomical, Observers in the Southern Hemisphere. 



Why should we go to the southern hemisphere in order to w T ork 

 upon this problem ? 



Were our object planetary research the inducement for another 

 southern observatory might not be sufficient. All the planets can 

 be seen from either hemisphere, and from either the whole fabric of 

 planetary astronomy could be constructed without help from the 

 other, though there would be undoubted advantage in cooperation. 



But in stellar observation the case is different. Nearly one- 

 quarter of the entire celestial sphere is inaccessible to exact observa- 

 tion from the observatories of the northern hemisphere. If we need 

 observations of the nebulae and stars in that part of the sky, we must 

 go to the southern hemisphere to get them. For many of the most 

 delicate researches fully one third of the sky should be under obser- 

 vation from the southern hemisphere. 



