128 CARNEGIE INSTITUTION 



receive great weight. It is then, according to my opinion, the best 

 economy of time and money to provide the observing station with 

 equipment of the first rank. Your proposition that the same instru- 

 ment should be employed alternately north and south of the equator 

 will help us to eliminate many errors from the star places. Con- 

 cerning the nature of the instrument, I should, for the declinations, 

 in place of the meridian circle, prefer a vertical circle of moderate 

 dimensions — 5-inch aperture. The vertical circle seems to me, for 

 a new observing station, preferable also from this point of view, that 

 the consolidation of the instrumental piers, which for a meridian 

 circle requires a long time, is for the vertical circle of no importance. 



As corresponding in accuracy to the declinations determined in 

 such manner, the right ascensions should also be observed with a 

 transit instrument. This part of the work could without inconveni- 

 ence be made at another station, at Cordoba, or in Australia. 



For the observations of the stars of the secondary catalogues, the 

 instrument described by you will certainly do good sendee. 



I submit these, my ideas, to your judgment, and I should be glad 

 if you find them worthy of any attention. 



I have delayed the answer of your letter until Dr. Backlund's 

 return from a journey in Germany. 



{From Director O. Backlund, of the Imperial Observatory , Pidkova.~\ 



[Translation.] 



Pulkova, August 20, 1 go j. 



In order to make my answer to your valued communication more 

 intelligible, I premise the following remarks : 



Fundamental determinations of star positions stand in the first 

 rank among the chief undertakings of the Pulkova Observatory. 

 To this end W. Struve had the transit and vertical circle con- 

 structed, by means of which the positions of the so called Pulkova 

 " Hauptsterne," 381 in number, have been determined in three 

 series, namely, at the epochs of 1845, 1865, and 1885 (about). 

 In the year 1894, in accordance with a plan by Nyren, the pro- 

 gram of the two instruments was enlarged by Bredichin so that 

 about 1,000 additional stars of the fourth to seventh magnitudes 

 should be determined for the epoch 1900, in general after the 

 same program as for the ' ' Hauptsterne. ' ' This series of observa- 

 tions is now completed. When I undertook the directorship, in 



