5IO POPULAR SCIENCE MONTHLY. 



THE AEEQUIPA STATION" OF THE HAEVAED 



OBSEEVATOEY. 



By Professor SOLON I. BAILEY, 



DIRECTOR OF THE AREQTJIPA STATION. 



THE same restless energy which impelled the American people to 

 become a world-power has led their men of science to extend the 

 range of their 'researches. The possibilities of a nation's influence 

 are bounded only by the whole earth ; and in a similar way the field of 

 astronomy is limited only by the whole sky. At the latitude of Cam- 

 bridge, Mass., an observer can never see more than three fourths of the 

 sky. In order to observe the remaining fourth, which lies about the 

 south pole of the heavens, he must seek some station below the equator. 

 A complete study of all the stars in the sky is imperatively demanded 

 for the solution of many of the great questions which the astronomy 

 of the future must answer. Only by bringing such completeness into 

 astronomical research will the construction of the universe and the 

 true place of our solar system become known. 



The Arequipa Station of the Harvard College Observatory owes 

 its foundation to the far-sighted policy of its present director. Pro- 

 fessor Edward C. Pickering. Under his direction, in 1889, the writer 

 of this article visited South America in order to make the preliminary 

 studies necessary to the selection of a station for the observation of 

 the southern sky. The west coast of South America was chosen for 

 this purpose, since it offered the possibility of great altitude, in addi- 

 tion to a dry climate and a clear atmosphere. The funds for this 

 enterprise had been bequeathed for such a purpose by Uriah A. Boyden, 

 a Boston engineer. 



From the best information which could be obtained in the United 

 States, it was thought that the valley of the Eiver Eimac, near Lima, 

 Peru, would furnish conditions favorable for the proposed station. 

 The valley itself, however, did not offer a sufficiently free horizon, 

 being shut in everywhere by mountains. There was a wide range for 

 choice in regard to elevation. The hills near Lima are only a few 

 hundred feet in height, while the great mountains forming the western 

 Andes rise eighteen thousand feet above sea level. The primary con- 

 ditions were an open horizon and a clear sky. To obtain a free horizon 

 it was only necessary to climb one of the steep and barren summits near 

 the valley; but to determine where the sky was clearest was a more 

 difl&eult problem. At this latitude the western Cordillera extends 



