1895. ] NEW YORK ACADEMY OF SCIENCES. 30 
Prof. Harold Jacoby then read a paper received too late for 
announcement in the Bulletin, on ‘Suggestions as to the deter- 
mination of the relative mass of the two components of the 
double Star, Eta Cassiopeiz, from Rutherfurd photographic 
measures.’ Prof. Jacoby outlined the method to be pursued in 
this investigation, and deduced the formuls to be used. The 
calculations will be made by Dr. Davis, The paper was dis- 
cussed by Prof. Rees. 
Prof. Pupin then explained a method of measuring alternating 
currents with a galvanometer. In consists in placing in the 
circuit a primary cell and an electrolite cell, whose counter 
electro-motor force is slightly greater than that of the primary 
cell. Under this condition only one-half of the alternations 
passed through the circuit, the other half being stopped by the 
two cells. Experiments have shown the availability of this 
method up to 600 alternations per minute. 
Prof. A. M. Mayer nominated Prof. E. R. Van Nardroff for 
resident membership, and the nomination was referred to the 
Council. 
The Academy then adjourned. 
J. F. Kemp, Secretary. 
SUGGESTIONS AS TO THE DETERMINATION OF 
THE RELATIVE MASSES OF THE TWO COM- 
PONENTS OF THE DOUBLE STAR ETA 
CASSIOPEILZ FROM RUTHERFURD 
PHOTOGRAPHIC MEASURES. 
By Haroup J AcoBY. 
The recent publication by the Academy of Rutherfurd’s 
measures of sixty-two stars about Eta Cassiopeiz, reduced by 
Dr. Davis, leads me to suggest that these same measures offer 
the possibility of computing the relative masses of the two com- 
ponents. There is a considerable probability that such a com- 
putation will lead to a successful result; and as we have at 
present only the discussion of this point by Mr. Ludwig Struve, 
a new investigation will be very interesting and important. It 
