ASTRONOMY — CAMPBELL, NEWCOMB. 173 



(b) The Crossley reflector photographs of Eros have been under con- 

 tinued measurement and reduction during lo months of the year, by Professor 

 Perrine, with the assistance of IMisses Chase and Hobe. The second half 

 of taking differences of measured distances, forming means and checking for 

 the plates measured, has been completed, and all the measures have been 

 reduced to standard rectangular coordinates. All the star positions, with the 

 exception of those on one date, have been reduced to mean places for 1900.0, 

 using the star-places supplied by Mr. Hinks, Chief Assistant, University 

 Observatory, Cambridge, England. The reductions to apparent place, the 

 parallax corrections, and the parallax factors have been computed, and the 

 positions of Eros interpolated from the ephemeris. The meridian observations 

 of Eros have been completely reduced and compared with the ephemeris for 

 the purpose of determining the systematic corrections to the ephemeris. 



At present a new reduction of the parallax plates to mean place is in prog- 

 ress, using a different grouping of the comparison stars. This will serve 

 the double purpose of testing two different methods of reduction and of sup- 

 plying an independent check on the accuracy of the calculations. 



Newcomb, Simon, Washington, District of Columbia. Grant No. 409. In- 

 vestigations ill mathematical astronomy, statistical methods, and eco- 

 nomic science. (For previous reports see Year Book No. 2, p. xxi ; 

 Year Book No. 3, p. 90; Year Book No. 4, pp. 83-84, and Year Book 

 No. 5, p. 88.) $5,000. 



Discussion of the Mean Motion and other Elements of the Moon from 

 Eclipses and Occnltations from the Period of the Earliest Babylonian Records 

 to the Present Time. — ^This work has been almost suspended for a year, 

 but is now again taken up with the intention of bringing it to completion as 

 soon as possible. Although the immediate object of the work is the history 

 of the moon's motion, this is by no means the sole important object. It 

 is anticipated that it will result in a more accurate determination of some 

 of the fundamental elements of astronomy, especially the motion of the sun 

 and of the ecliptic and the absolute right ascensions of the fundamental stars. 



Investigation of the Action of the Planets on the Moon. — This work was 

 pviblished in June last. A great mass of test computations w^ere necessary 

 while it was going through the press, and this occupied most of the time 

 during the first four months of the year. 



Investigation of Terrestrial Temperatures, to Determine zvhether they are 

 Affected by Variations in the Sun's Radiation of Energy. — This work was 

 brought to completion and made ready for the press in June last, but still 

 awaits publication by the American Philosophical Society. It embraces a 

 discussion and comparison of fluctuations of temperature in various widely 



