OF ARTS AND SCIENCES. 551 



changes of Europe, from 350 to 1100 A. D., illustrated by a 

 series of seventy-five colored maps, showing the boundaries 

 of each tribe and nation for every ten years. 



The following announcement by Henry Taber was read 

 by William E. Story : — 



In Volume XVI, p. 130, of the American Journal of Mathematics 

 I have shown that certain conditions are satisfied hy every orthogonal 

 substitution which is given by the positive square of Cayley's symbolic 

 expression for orthogonal substitutions, in other words, by every 

 orthogonal substitution which is the second power of an orthogonal 

 substitution. I have since found that these conditions are sufficient 

 that a given orthogonal substitution shall be the second power of an 

 orthogonal substitution. 



"»■- 



The following papers were read by title : — 



On the Action of Ammonia upon Cupriammonium Aceto- 



bromide. By Theodore W. Richards and Robert J. Forsyth. 

 Velocity of Electric Waves. A direct Determination of 



this Value and a Discussion of its Relation to the Velocity of 



Light. By John Trowbridge. 



Eight hundred and seventy-fourth Meeting. 



April 10, 1895. — Adjourned Stated Meeting. 



The President in the chair. 



In the absence of the Recording Secretary, William R. 

 Livermore was appointed Secretary pro tempore. 



The chair announced the death of James Edward Oliver, 

 of Ithaca, Associate Fellow. 



The Corresponding Secretary read a circular from Emil 

 Diebitsch, soliciting on behalf of Mrs. Josephine Diebitsch 

 Peary subscriptions in aid of a proposed expedition for the 

 relief of Mr. Peary and the promotion of Arctic scientific 

 research. 



On the motion of B. A. Gould, it was 



Voted, That the Corresponding Secretary be directed to 

 express to Mrs. Peary the regrets of the Academy that the 



