IO 



observatory may hope to cover the ground com- 

 pletely, it may reasonably expect to contribute 

 toward the solution of the problem and thus to aid 

 in attaining a clearer comprehension of that great 

 process of evolution which has produced the earth 

 and its inhabitants. It is evident, from the nature 

 of the case, that the plan of attack must be broad 

 and elastic, utilizing a variety of powerful methods 

 toward a common end. But in the presence of 

 innumerable interesting objects for study, there is 

 danger of a scattering of effort and a mere multi- 

 plication of observations. Every possible astro- 

 nomical observation might have a bearing on our 

 problem and thus seem to justify its making; but 

 unless it were made as an element in some general 

 plan, an indefinite amount of energy might be 

 spent without avail. A common scheme should 

 tie together many diverse investigations, multi- 

 plying the intrinsic importance of each because of 

 its bearing on all the others. 



THE SUN. 



Let us begin with the sun. Its prime interest 

 and importance, as the source of the light and heat 

 on which we all depend, would be sufficient reason 

 for its special consideration. But equally signifi- 

 cant is the fact that the sun is the only one of all the 

 stars which lies near enough to the earth to be 

 studied in detail; each of the others is reduced by 

 distance to an infinitesimal point of light, which the 

 most powerful of telescopes can not magnify into an 



