124 CARNEGIE INSTITUTION 



places of the heavenly bodies and of the great constants of astron- 

 omy as to induce an organized effort to investigate its character in 

 the most complete and precise way. A large number of series of 

 observations has been made during the last seven or eight years 

 with the special object of determining the actual variations of lati- 

 tude in various quarters of the world. Recently, upon the initiative 

 of the German Geodetic Association, international observing sta- 

 tions, suitably distributed upon the same parallel of latitude, have 

 been occupied by astronomers. Such a station has been established 

 atGaithersburg. Md., and at Ukiah, California ; and another is pro- 

 vided b3/ the Observatory at Cincinnati. It has been strongly urged 

 that similar stations should be established in the southern hemi- 

 sphere. This is a subject which is well worthy the attention of our 

 govertiment, and should be urgently pressed for its favorable con- 

 sideration. It is quite possible that in the future this subject in 

 some of its phases may deser\'e serious consideration by the Carne- 

 gie Institution. 



Astronomical Constants. 



None of the great constants of astronomy is yet determined with 

 the accuracy which modern science demands. In recent years the 

 solar parallax has demanded an amount of attention which seemed 

 at times disproportionate to that which was devoted to other impor- 

 tant fields of astronomical effort. The support which was extended 

 by governments to expeditions for the observation of transits of 

 Venus in 1874 and 1882 was munificent beyond precedent, and 

 probably beyond the actual requirements of the case. Our govern- 

 ment was even more liberal than any other. It is not known 

 whether the observations by parties sent out from the United States 

 were ever completely reduced. Twenty years after the last transit 

 find them still unpubhshed. 



Meanwhile other methods for the determination of the solar par- 

 allax ha-v'e been applied, apparently with a result worthy of greater 

 confidence than that due to observations of transits. Nearly a 

 quarter of a century ago Gill employed the heliometer with good 

 result in observations upon Mars at Ascension Island. Later, Gill 

 and others employed the heliometer in cooperating observations 

 upon minor planets favorably situated for the determination of par- 

 allax. The constant which is generally adopted at present virtually 

 rests upon these observations. A few years ago a new planet, Eros, 

 was discovered, remarkable for its eccentricity and its occasional 



