130 CARNEGIE INSTITUTION 



our knowledge of motions in the planetary system and in the stellar 

 field. 



That the observations, especially those which concern the declina- 

 tions, should be made, if possible, under a southerly latitude of at 

 least — 40°, I am in agreement with Nyren. As to that which per- 

 tains to the planning of instruments, in consideration of the high 

 degree of technical skill in the construction of instruments in America, 

 it might appear venturesome to express decided opinions from here. 

 I content myself with calling attention to the experience which we 

 have gained here in Pulkova and in Odessa with the transit and 

 vertical circle as to the determination of right ascension and declina- 

 tion with special instruments. 



If, in addition to the fundamental determinations, the projected 

 zone observations can also be secured, you will in that way earn the 

 thanks of astronomers for all time. 



There can be no doubt that the derivation of astronomical con- 

 stants from obser\^ations in the southern hemisphere is a thing to be 

 desired. For example, the very discordant values of the aberration 

 constant, which the determinations secured at different observatories 

 have recently shown, prove how necessary classic observations are. 

 Latitude variations demand observations at places separated from 

 one another as widely as possible. In accordance with an agreement 

 with Potsdam, a series of observations for this purpose will be un- 

 dertaken here in Pulkova, and with a zenith telescope of 5 inches 

 aperture. 



In regard to your remaining questions, so far as I may be per- 

 mitted to judge, they are not less rationally proposed. You will be 

 able to count upon the unanimous approval of the scientific world 

 not less for these than for the others. 



That the existing arrears in astronomical work in the southern 

 hemisphere is felt as a drag at every step in every investigation now 

 in progress cannot be denied. If on that account the investigation 

 planned by you is realized, then a great drawback will be thereby 

 removed ; but the well known American energy affords a warrant 

 that the carrying out of this plan will not be long delayed. A speedy 

 realization of this project means an immense advance in science. 



