LXXVI THE ROYAL SOCIETY OF CANADA 
As the extra-focal method seemed best adapted to variable star 
work, the light curves of spectroscopic binaries, especially of those 
whose orbits have been determined here, are being investigated. 
The programme includes 50 Draconis, ¢ Geminorum, 6? Tauri, 
b Persei, 18 Aquilae, 6 Librae and 12 Lacertae. The last shows 
strong evidence of light variation and will be closely followed; 50 
Draconis also shows signs of variability. 6 Librae is being observed 
to improve the present light curve. Work on the others has not been 
carried sufficiently far to warrant any statement. 
SOLAR INVESTIGATIONS 
Direct photographs of the sun, 35 in number were obtained on 
suitable days when spots were present, but this work was stopped 
for some time to permit of repairs to the shutter. With the coelostat 
telescope and solar spectrograph 330 plates were obtained. These 
include series, taken at several different wave-lengths, of spectra 
of centre and limb simultaneously and in some cases with a comparison 
spectrum of iodine absorption added. A number of plates of sun 
spot spectra were also made. 
The plates for the determination of the solar rotation made in 
1911, 1912 and 1913 were finally reduced and discussed and the 
summarized results published in the Astrophysical Journal. They 
are now being prepared for final publication in the Dominion Obser- 
vatory Publications. The results of all these years are in close agree- 
ment, although there seems to be slight evidence of decreased values 
in 1913, but not more than can be explained by change in habit of 
measurement. 
A special series of plates around the equator in the region near 
the D group, where atmospheric absorption lines enabled instrumental 
errors to be eliminated, gave strong evidence of a short period varia- 
tion in the solar rotation, and the lower value in 1915 than in 1913 
showed also possibility of a secular change in the rate. Two other 
interesting researches on ‘‘Measurements of Blended Spectra’’ and on 
“The Psychology of Differential Measurements,”’ bearing on the results 
obtained in the measurement of solar spectra, have recently been 
published in the Journal of the Royal Astronomical Society of Canada. 
MERIDIAN OBSERVATIONS 
Observations with the meridian circle were obtained on 121 
nights; there were about 2,700 observations for right ascension and 
and 1,600 for declination; the work with this instrument was devoted 
mainly to the list of latitude stars which has been under observation 
for several years. 
