1893. ] NEW YORK ACADEMY OF SCIENCES. 121 
tion of the parallax of this star was begun at Potsdam in the 
autumn of 1890. In the course of the reduction of these meas- 
ures it was found that certain discordances existed between the 
parallaxes derived from different comparison stars. These dis- 
cordances could not be accounted for on the ground of errors of 
observation, nor did the measures of the comparison stars 
themselves show evidence of a difference between their own re- 
spective parallaxes. Dr. Wilsing was, therefore, led to suspect 
the presence of one or more unknown bodies in the system, and 
to investigate by observation the effect upon the distance be- 
tween the two visible components. Great care was taken to 
eliminate from the results all sources of error known to affect 
photographic observations, and the reductions were carried out 
with all necessary precision. The series of observations ex- 
tended from 1890, October, to 1893, September. <A table is 
given showing the results suitably grouped in means. They 
have all been corrected to 1891 .0 for proper motion by assum- 
ing that the continuous yearly increase of the distance is 0. ’10. 
A comparison of the numbers in the table shows that the 
systematic differences are too large in comparison with their 
probable errors to be taken as the result of errors of observa- 
tion. Dr. Wilsing gives also a graphical representation of the 
observations by means of a curve. He concludes finally that 
the distance of the two visible components of 61 Cygni is sub- 
ject to a fluctuation as great as 0. 73, and having a period not 
far from 22 months. Systems of this kind, he thinks, offer a 
connecting link between the spectroscopic and visual binary 
systems. 
Mr. Harold Jacoby also read : 
‘““Some recent papers on the reduction of astronomical photo- 
graphs.”’ 
This paper will be contributed to the Astronomical Journal. 
Professor Rees gave a brief account of the work now being 
carried on for making a photographic catalogue and a chart of 
the heavens. His remarks were illustrated by lantern slides 
showing the photographic telescopes and the measuring micro- 
meters used for the purpose. 
Mr. Post exhibited a number of plates of the Pleiades and 8 
Cyegni which he had made at his observatory at Bayport, L. I. 
He intended to measure these plates, in order to compare their 
accuracy with that attained by Rutherfurd and other astronomers. 
