Il6 CARNKGIE INSTITUTION 



the University of Pennsylvania and elsewhere, as well as at various 

 observatories in Europe and the southern hemisphere, have been 

 directed with good effect upon this work ; so that there is no reason 

 to complain of a deficiency in this class of observations. The part 

 borne by America in this campaign is extremely creditable and in 

 most refreshing contrast to the historj^ of American astronomy in 

 this respect previous to 1870. In comparison with other branches 

 of astronomical work, the need for increased activity in this line is, 

 perhaps, relatively less pressing. 



Researches upon the System of the Stars. 



Under this general head may be included a very important part of 

 the work of astronomers of the present da3\ We may construe it as 

 including meridian and other observations for the position and mo- 

 tion of stars ; observations to determine astronomical constants, 

 such as refraction, aberration, and nutation ; observations for varia- 

 tion of latitude ; determination of parallax, and a great variety of 

 researches which require fundamental observations of precision as 

 the basis. Included in this class of investigations also are meridian 

 observations of planets, upon which our planetary theories are based, 

 since such observations must be made in the same way and in the 

 same series as those of high precision upon the stars. 



Observations for Positions of Stars. 



There are more than twenty-five observatories in the world 

 wherein observations to determine the positions of stars form the 

 principal activity. There are as many more observatories where 

 such observations are an important part of the work undertaken. 

 At the great national observatories located at Pulkowa, in Russia ; 

 Greenwich, in England ; Paris, in France, and Cape of Good Hope, 

 in South Africa, in some form or other, such observations are the 

 chief employment, and the fame of those institutions rests chiefly 

 upon what they have accomplished in observations of this class. 



We have first exploratory and statistical observations where iden- 

 tification and enumeration are the principal objects to be attained. 

 The great Durcluuusterung carried out at the Bonn Observatory by 

 Argelander and Schonfeld, the similar survey undertaken at the 

 Cordova Observatory, in the Argentine Republic, and the photo- 

 graphic survey completed at the Cape of Good Hope are the leading 



