366 
PHILOSOPHICAL SOCIETY OF WASHINGTON. 
President . 
Vice-Presidents . 
Treasurer . 
Secretaries ..... 
.. C. D. Walcott. 
f R. Rathbun. 
1 J. H. Gore. 
.. B. R. Green. 
.. J. F. Hayford. 
C. Adler. 
E. D. Preston. 
C. K. Wead. 
General Committee. 
L. A. Bauer. 
W. A. DeCaindry. 
J. G. Hagen. 
G. W. Littlehales. 
I. Winston. 
C. F. Marvin. 
H. M. Paul. 
F. W. True. 
J. E. Watkins. 
527th Meeting. January 5, 1901. 
President Walcott in the chair. 
Thirty persons present. 
Mr. Eimbeck presented informally the question of an appar¬ 
ent error arising in transit observations from the fact that at a 
locality where there is local attraction of the plnmb line the 
geodetic and astronomical meridians differ sometimes as much as 
30". 
Mr. I. Winston read a paper on The thirteenth general confer¬ 
ence of the International Geodetic Association, held at Paris last 
fall, at which 17 countries were represented. The principal 
papers there presented dealt with recent work at gravity-stations, 
the question of variation of latitude, the proposed revision of 
older triangulations in France and Peru, the nickel-steel alloy 
with small coefficient of expansion, and the recent and prospect¬ 
ive measurements of terrestrial arcs. [Published in Science, 
vol. xiii, p. 129 (1901).] 
In the following discussion Mr. C. A. Schott gave an histor¬ 
ical account of such arc measurements and their results, pointing 
out that the Clarke spheroid agreed better with the IJ. S. obser¬ 
vations thus far reduced than the Besselian; and Mr. Hayford 
described more fully Cornu’s simple and ingenious apparatus for 
