112 CARNEGIE INSTITUTION 



of expedition is in the minds of the Committee, and it seems to me 

 to be most attractive, and to promise an economical solution of the 

 problem of dealing adequately with the southern hemisphere on 

 lines suggested by a study of past history. 



[^froin Director M. Locwy, of the Paris Observatory , President of the 



Congress for the Carte du CielJ\ 



[Translation.] 



Paris, ftdy 20, igoj. 



The establishment of two observ^atories in the southern hemi- 

 sphere would be, without any doubt, of high utilit^^ for astronomy. 



The program prepared by the Committee in regard to the work to 

 be accomplished there, seems to me, in its broad lines, most judi- 

 cious. You have expressed in your communication two ideas which 

 are in perfect harmony with my own personal view : First, that 

 large scientific enterprises often stand in intimate relation with each 

 other, which brings it to pass that the success of the one insti- 

 gates progress in the others ; Second, that it is desirable to have at 

 our disposal a la'-ge number of carefully determined proper motions 

 in order to undertake with profit some of the noblest problems which 

 today are occupying the minds of the most eminent astronomxcrs. 

 It is only in this way that one can acquire more precise conceptions 

 of the nature of the trajectory- of our solar system and of the gen- 

 eral structure of the universe. I take this point of view in com- 

 municating to you the reflections suggested by a perusal of the 

 program of the committee. 



First of all, I should like to suggest a slight modification of j^our 

 plan of work concerning the execution of the meridian observations 

 between — 32° and — -90° of declination, in order to give to this re- 

 search a more general utility and to render it valuable in the con- 

 struction of the Astrographic Chart. In order that you may better 

 appreciate the drift of the remarks which I submit to you, allow me 

 to present some explanations concerning the details connected with 

 this work. The recent researches which I have published on the 

 subject of the precision with which one can take the astronomical 

 coordinates of the stars from a photograph show that by exercising 

 the necessarj^ precaution one can attain such precision that the total 

 probable error would reach at the maximum ±: o."2 even for the 

 faintest images. This determination is not in the given instance an 

 optimistic estimsLte; it represents the reality. It is well to add that 



