DOEPAT AND POULKOVA. 385 



The activity of tlie Central Observatory lias doubtless suffered somewliat from 

 tlie restricted communication between Poulkova and the neighboring cities, St. 

 Petersburg and Tsarskoe-Selo. Foi-, however much this isolation favors the 

 undisturbed prosecution of obsen-ations and study, it imposes a dreaded monot- 

 ony upon the lives of the non-astronomical portion of the community, from the 

 effects of which the astronomers themselves cannot be entirely free. To coun- 

 teract the influence of this sameness — so prejudicial to mental and physical 

 health, and so detrimental to the harmony of society — requires the constant 

 attention of each individual living at the observatory. It will tluis bo easily 

 understood that the personal example and the influence of the director as a man,* 

 no less than his experience as an astronomer, are needed in order to secure the 

 happiest working of all the parts. Possibly the sameness of the social circle 

 exaggerates the influence of the monotony of the astronomical work, for there is 

 in Poulkova no rotation of duties, such as in some other observatories affords a 

 slight relief to tho members of the corps. 



It was in accordance with Struve's foresight that the efforts of the observatory 

 to realize its general object, "the advancement of astronomy as a science," 

 should l>e principally confined to stellar astronomy, and that to each astronomer 

 should be assigned the instruments needed for the work undertaken by him,, 

 and for whose execution he is responsible, thus reversing a very common prac-- 

 tice of assigning tho observer to an instrument. The description of the instru- 

 ments and the mode of using them may be found fully given ii^the well knowTi 

 ''Descriptit)n de I'observatoire." The following condensed notice of the progress 

 of the works there indicated as having been begiui will perhaps have interest. 

 The Great Refractor, made by Frauenhofer, in tho central dome, has, since its 

 erection, been used principally by the present director. The general survey in 

 1841 of the northern heavens, requiring the examination of 17,000 stars, and 

 leading to the discovery of nearly 500 new double stars, has been already men- 

 tioned. Up to the present time micrometric obsei"\'ations of relative ]iositions- 

 have been made upon 1,200 double stars, which will probably be published in 

 1SG9 in all their details. Struve's method of observing position angles, i. e., 

 by placing the two parallel threads of his micrometer so that the space included 

 between them is bisected by a line joining the two stars, leads probal)ly to the 

 interesting systematic errors in observed angles of position, investigated ])y him 

 in 1852-56, and again in 186(3, by observations upon artificial double stars. 

 In the latter year an investigatiou was also made of the errors of estimated 

 small distances, and a simple systematic correction deduced, by which these 

 become as valuable as actual measurements with the micrometer. Nine optically 

 double stars have been made the subjects of special investigations for relative 

 ^parallax. The determinations of relative positions of comets and faint com- 

 j)arison stars have next claimed attention. The series upoy the Biela's, Faye's, 

 and Donati's comets, and those of 1861 and 1865-66, are to be specially men- 

 tioned, as also the fruitless search after Biela's comet at its late predicted return. 

 The observations of Neptune's satellite and the determination of the planets' 

 mass have been already mentioned ; a large number of observations upon the 

 eatellites of Uranus and Neptune still await publication. The occupations of the 

 Pleiades, in which a dozen observers sometimes combine, have been regularly 

 continued. The study of Saturn's rings and of the great nebula in Orion have 

 also claimed attention whenever circumstances have conspired to favor the jiros- 

 ecution of these very delicate observations. The results already attained, and 

 their comparison with those of the Bonds at Cambridge, are already well known 

 to the world. The instrumental chanii^es made in tho p-reat refractor have been 

 quite msignmcant ; but on account of increasing unsteadiness in the parallactic 

 movement the director has proposed to replace the clock-work by some one of 

 the improved mechanisms now made. This will become the more necessary in , 

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