140 CARNEGIE INSTITUTION 



brightness is very considerabl}^ reduced, especially iu the case of 

 the somewhat fainter stars. Thereby the personal error depending 

 on brightness must be changed and an element of uncertaint}^ intro- 

 duced into the right ascensions. If I am not mistaken, the effect was 

 found to be quite perceptible in Leiden. 



As the elimination of systematic error influenced by refraction 

 and flexure is of such paramount importance for our fundamental 

 declinations, I would suggest to supplement the above determina- 

 tions by the determination of some hundreds of fundamental decli- 

 nations by the method explained in Copernicus III, pages 147-182, 

 which make the result absolutelj^ free from both refraction and 

 flexure. ^ ^ ^ 



(3) Determination of Radial Velocities. 



I have no suggestions to add to the plan developed in the ' ' con- 

 fidential statement," with which I most cordially agree, as far as I 

 can judge of the matter. 



P. S. — In regard to the measurement and reduction of the plates 

 for a Parallax Durchmusterung, which might perhaps be considered 

 to put too heavy a strain on a single observatory, I would like to add 

 that no doubt many of the smaller observatories, not too well pro- 

 vided for, would be only too glad to do the work of first class im- 

 portance by measiiring and reducing good parallax plates. Under 

 certain conditions the laboratory at Groningen would very willingly 

 undertake the complete work of measuring reduction and description 

 for a duplicate set of plates for a zone of 2° width at least. 



[From Dr. Arthur Auwers, Secretary of the Royal Prussian Academy, 



Berlin 7\ 



[In a private letter to the chairman Dr. Auwers discusses various topics. 

 The following extracts refer to the plan for a proposed observing station in the 

 southern hemisphere.] 



[Translation.] 



Greifswald, October 6, igoj. 

 The "confidential statement" enclosed in your letter of Jul}' 7 

 designates the most pressing astronomical tasks to be worked out in 

 the southern hemisphere so fully and, according to my judgment, so 

 much to the point, that I find very little to add thereto; and, fur- 

 thermore, my pressing work has hindered me until now from pre- 



