488 
PHILOSOPHICAL SOCIETY OF WASHINGTON. 
500th Meeting. April 15, 1899. 
The 500th meeting of the Society was celebrated by a dinner 
at Rauscher’s, corner Connecticut avenue and L street. 
There were present F. V. Coville, President of the Biological 
Society; H. N. Stokes, President of the Chemical Society, and 
the following members: 
Cyrus Adler. 
Marcus Baker. 
F. H. Bigelow. 
Rogers Birnie. 
J. W. Chickering. 
F. W. Clarke. 
,T. R. Cook. 
Whitman Cross. 
W. H. Dali. 
W. A. De Caiudrv. 
J. R. Eastman. 
Louis A. Fischer. 
J. M. Flint. 
J. Howard Gore. 
B. R. Green. 
J. G. Hagen. 
William Harkness. 
J. F. Hayford. 
H. L. Hodgkins. 
A. F. A. King. 
A. Lindenkohl. 
W J McGee. 
S. Newcomb. 
H. G. Ogden. 
James Page. 
E. D. Preston. 
H. S. Pritchett. 
G. R. Putnam. 
Richard Ratlibun. 
G. M. Sternberg. 
0. H. Tittmann. 
F. W. True. 
C. D. Walcott. 
J. E. Watkins. 
C. K. Wead. 
Isaac Winston. 
C. C. Yates. 
501st Meeting. April 29, 1899. 
Vice-President Pritchett in the chair. 
Thirty-three members present. 
Mr. Preston made an informal communication on Recent 
geodetic operations in Spain, dwelling particularly on the meas¬ 
urement of base lines and the geodetic connection between Spain 
and Algiers. [Not published.] 
Discussed by Messrs. Gore and Dall. 
Mr. Hayford read a paper on A new treatment of refraction 
in height computations. [For brief abstract see Science, 1899, 
May 12, new series, vol. ix, no. 228, p. 686.] 
Discussed by Messrs. Harkness, Hayford, Pritchett, Pres¬ 
ton, Paul, Wead, and Moore. 
Mr. Pritchett read a paper entitled An estimate of the popu¬ 
lation of the United States in 1900 derived from an empirical 
