Astronomical Observatories 

 bal, Santiago, Chile. It is used to secure spectro- 

 graphic observations of stars not visible from sta- 

 tions in the northern hemisphere. The D. O. Mills 

 Observatory is administered by the director of the 

 Lick Observatory. 



It was Mr. Lick's intention that the observatory 

 should be made "useful in promoting science." A 

 brief review of the work accomplished there since 

 1888 shows that the scientific staff has been faithful 

 to the trust reposed in it. To make new discoveries, 

 in the ordinary sense of the phrase, is not the chief 

 function of an astronomical observatory. On the 

 contrary, all great observatories devote their ener- 

 gies principally to carrying out large programs of 

 work, often requiring many years for their com- 

 pletion, which have been carefully planned to aid in 

 solving definite problems relating to the structure 

 and the evolution of the solar system and of the 

 sidereal universe. Discoveries in the usual sense 

 are, however, the inevitable by-products of such 

 researches and the Lick Observatory has many of 

 these to its credit. Thus, its astronomers have dis- 

 covered 4 new satellites to Jupiter; 19 unexpected 

 comets, and 10 periodic comets whose return had 

 been predicted; 4400 double stars; 250 spectro- 

 scopic binary stars, and many hundred new 

 nebulae. 



The first great successes in photographing comets 

 and the Milky Way were made there, and the un- 

 equaled Lick series of comet photographs has taught 

 us more about the structure and formation of 

 comets' tails than had been learned in all previous 

 time. The photographs of the minor planet Eros led 

 to a new and accurate determination of the earth's 

 distance from the sun. The photographs of nebulae 

 and star clusters made with the Crossley reflector 

 established for the first time the tremendous ad- 

 vantage of this form of telescope in photographing 

 such objects, with the result that many reflecting 

 telescopes of equal or of greater power are now in 

 use, or in process of construction, at other observa- 

 tories. The photographs materially changed our 

 ideas of the nebulae. Some 10,000 nebulae had pre- 

 viously been discovered, of which a few dozen, 

 supposed to be exceptional, were known to be 

 spiral in form. The Crossley reflector photographs 

 showed that many other known nebulae were 

 spiral, revealed hundreds of new nebulae, and 

 proved that the majority of them have the spiral 

 form — undoubted evidence of their rotation. 



A systematic survey of the northern sky has 

 been carried out with the 36-inch and 12-inch re- 



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