1=2 CARNEGIE INSTITUTION 



seriously undertaken by Professor Pono at Turin and Dr. H. S. 

 Davis in this country. Th.e latter has been aided by the Trustees 

 of the Gould fund. The question whether anything to promote 

 the work can be done by the Carnegie Institution is respectfully 

 submitted. 



4. Attention has recentl}- been called by Professor Rarabaut to a 

 lemurkable .series of observations made by Professor Hornsby at the 

 Radcliffe Observatory, Oxford, beginning in 1774, which he is de- 

 sirous to reduce. From iiis report it would seem that the results 

 may be of special value. It therefore seems desirable to investigate 

 the question of their precision and of the character of the results to 

 be derived from them. When this is done the question of provid- 

 ing for their complete reduction could be considered. 



Respectfully submitted. 



Simon Newcomb. 



Washington, Octobers, 1902, 



Appendix F to Report of Committee on Astronomy. 



PROGRESS AND PRESENT STATE OF CELESTIAL 

 PHOTOMETRY AND PHOTOGRAPRY. 



By E. C, Pickering. 



Celestial Photometry. 



The earliest estimates of the relative brightness of stars are recorded 

 by Ptolemy in the Almagest, but careful comparisons, capable of 

 revealing small changes in brightness, were first made by Sir Wil- 

 liam Her.^-.chel. The inadequacy of vi-sual estimates was recognized 

 b}'' Sir John Herschel while engaged in extending and improving 

 his father's work. This led to the constructions of the first .stellar 

 photometer, by Vt^hicb the light of a star was compared with a minute 

 image of the Moon, adjustable in distance from the eye. The full 

 possibilities of comparisons made without instrumental aid for large 

 numbers of stars v/ere realized by Argelander, whose Uranoinetria, 

 Nova., giving the approximate magnitudes and places or 3,256 stars, 

 •was published in 1843. This was followed t^venty years later by 

 the inonumeatal Bonner Durchnitisteru?ig giving the positions and 

 magnitudes of 324,189 stars in the northern heavens, in the prepa- 



