370 PHILOSOPHICAL SOCIETY OF WASHINGTON. 
has been done, one party measuring about 63 kilometers in 6 
months to one part in 1,000,000; the principal United States 
and European stations had been connected by pendulum observa¬ 
tions ; various disconnected lines of precise levels had been con¬ 
nected, and a new dictionary of elevations of 4,000 places had 
been published. The calculations based on the United States 
measures indicate that the surface of the United States will 
agree with the Clarke spheroid of 1866 within 170 meters. [Pub¬ 
lished in this volume, p. 139.] 
A long and spirited discussion followed, participated in by 
Messrs. Gore, Marvin, Harris, and Baker. Questions were 
raised concerning the accuracy of the new base-line apparatus, 
and of the precise-leveling work, especially with reference to the 
relative elevation of the Gulf of Mexico and the Atlantic Ocean. 
531st Meeting. March 2, 1901. 
Vice-President Rathbun in the chair. 
Twenty-six persons present. 
The election and qualification of Messrs. R. L. Paris, Wil¬ 
liam Weinrich, Jr., and Walter G. Cady, all of the Coast and 
Geodetic Survey, were announced. 
Mr. Farqithar stated informally that eye observations on the 
Nova in Perseus showed marked variations in brilliancy; and 
Mr. Bauer stated that the Toronto magnetic observations at the 
time of the solar eclipse showed a slight disturbance coincident 
with the passage of the sun’s shadow. Analysis shows that the 
effect is due to causes outside the earth’s crust, and probably due 
to changes in the upper atmosphere caused by the passage of the 
shadow. 
Mr. J. G. Hagen presented a Report on progress in astronom¬ 
ical photometry. It considered (1) catalogues, noticing espe¬ 
cially the Harvard photometry and Osthoff’s catalogue of star 
colors; (2) original observations of variable stars, particularly 
those by Peek, Knott, and Pickering; (3) the physical explana¬ 
tion of variability; and (4) the new charts of variable stars, 
notably Pogson’s. The latter part of the report was illustrated 
by lantern slides. [Published in this volume, p. 151.] 
