144 KECOKD OF SCIENCJ': FOR 18S7 AND 1888. 



only two observatories that have thus far given systematic atteution 

 to this important line of work. The most interesting results are in the 

 case of Sirius, which, when first observed at Greenwich in the winter of 

 1875-'7G, seemed to be receding from us at the rate of 24 miles per 

 second. This recession gradually changed to an approach of 5 miles 

 per second in 1882-'S3, increasing to 24 miles in 1885-'S0, and then 

 dropping to 1 mile in 1886-87, and now becoming a recession again, in 

 1887, of 6 miles per second. As the Astronomer Royal remarks, these 

 results are to be accepted with caution; the F line for which the meas- 

 ures were made would seem to have changed somewhat its character- 

 istics, and the observation is moreover one of extreme difficulty, the 

 discordances obtained on different nights being almost as great as the 

 whole range of displacement noted. 



Dr. Vogel, of Potsdam, has successfully applied photography to the 

 determination of the displacement of Hues in stellar spectra due to a 

 motion of the star in the line of sight. Two Eutherford i)risms were 

 used, the observations being made on the third line of hydrogen, H;'. 

 Dr. Scheiner, who has been carrying out these experiments, has exam- 

 ined the spectra of Sirius, Procyon, Castor, Arcturus, Aldebaran, Pol- 

 lux, and Rigel. Of these, Sirius showed a slight displacement toward 

 the red, thus indicating a motion away from us; Procyon a decided dis- 

 ])lacement, and Rigel a very large one in the same direction, while Arc- 

 turus showed a considerable displacement towards the violet. A sys- 

 tematic examination of all stars of the first and second magnitudes is 

 to be undertaken with improved apparatus. 



ASTRONOMICAL PHOTOGRAPHY. 



The Paris International Astrophotographic Conf/ress. — The general in- 

 terest in the application of photography to astronomical observations 

 has resulted in a meeting called by the French Academy of Sciences, 

 at the instance of Admiral Mouchez, for the purpose of uniting upon 

 a plan for preparing by international co-operation a photographic 

 chart of the heavens more extensive than any hitherto attempted 

 by the usual methods. The Congress was opened at the Paris Ob- 

 servatory on April IC, 1887, by M. Flourens, minister of foreign af- 

 fairs of the French Government, and addresses were made by M. Ber- 

 trand, tlie eminent mathematician, by Admiral Mouchez, director of the 

 Paris Observatory, and by Professor Struve, director of the Pulkowa 

 Observatory. Fifty-six members were present, including thirty-seven 

 foreign astronomers, representing sixteen nations. Admiral Mouchez 

 was chosen honorary president; Struve, president; Auwers, Christie, 

 and Faye, vice-presidents; Bakhuyzen and Tisserand, secretaries, and 

 Duner and Trcpied, assistant secretaries. At the first meeting a com- 

 mittee of nineteen was appointed to consider and report upon the size 

 and construction of the instruments to be employed, and upon the limit 

 of star-magnitudes to be included in the photographs. This committee 



