REPORT OF COMMITTEE ON OBSERVATORIES 3 1 



a part of the uncertainties in our knowledge of astronomical refrac- 

 tion could be in a marked degree eliminated. The proof of this is 

 already at hand in numerous comparisons of observations made con- 

 temporaneously with different instruments in the two hemispheres. 

 From these it can easily be inferred what would be the probable gain 

 if both sets of observations were to be made with the same instru- 

 ment. We think that this plan presents a unique opportunity which 

 ought not to be neglected. 



If the meridian circle should be employed with a full corps of as- 

 sistants the southern work here proposed could probably be accom- 

 plished within four or five years from the date of beginning. It 

 would involve about 40,000 observations of about 6,000 stars and 

 about 4,000 observations of stars north of — 20° for the purpose of 

 comparison and check. From four to seven observers and com- 

 puters would be needed, with as many more routine computers, in 

 order to keep the work going continuously and the computations 

 up to date. 



(2) Complete Observation of Stars to the Ninth Magyiitude. 



The exact determination of the positions of telescopic stars down 

 to the ninth magnitude and south of — 30° of declination is a work 

 of high importance. The opinions of astronomers would differ as 

 to the pressing nature of this work in comparison with the two suc- 

 ceeding works mentioned in this schedule. As will be seen from 

 the correspondence transmitted herewith, there are opinions of great 

 weight equally positive in favor of each of these undertakings. The . 

 plan for meridian observation of faint stars is mentioned second in 

 order because of its intimate logical connection with the investiga- 

 tion already mentioned under (i). 



The project to observe with meridian instruments the precise 

 positions of all stars down to the ninth magnitude originated some- 

 what more than thirty five years ago, and was adopted as the pecu- 

 liar function of the Astronomische Gesellschaft , which at that time 

 assumed something of an international character. The importance 

 of this project has been universally recognized. The original pro- 

 gram for the northern hemisphere was completed under a coopera- 

 tive arrangement. The extension of this work under the same 

 auspices has been carried to — 22° of declination, and the observa- 

 ton,' at Cordoba has pushed the work on to — 32° of declination. 

 About one quarter of the sky remains to be considered. The com- 



