THE DOMINION ASTRONOMICAL OBSERVATORY AND 
THE BOUNDARY AND GEODETIC SURVEYS. 
The work of the Observatory has followed the same general lines 
as in previous years. 
In the Astrophysical Division, the principal work has been, as 
before, the determination of the orbits of spectroscopic binary stars. 
The elements of the orbits of six binaries have been completed during 
the year, b Persei, @ Tauri, ¢ Geminorum, y Geminorum,  Urse Majoris 
and d Bootis. @ Tauri is noteworthy on account of its being a com- 
ponent of the moving cluster in Taurus discovered and discussed by 
Boss. The velocity of the system as observed is in good agreement 
with the theoretically deduced velocity while the star is distant a light 
journey of about one hundred and forty years. + Geminorum is of 
special interest on account of its long period, the longest so far deter- 
mined, over six years, thus bridging the previously existing gap between 
spectroscopic and visual binaries. During the year 715 stellar spectra 
were secured, about 130 less than in the previous year. This decrease 
is in great part due to the fact that fainter stars have to be observed, 
requiring longer exposure times. 
The spectrographs have remained practically unchanged, no 
improvements having suggested themselves. A five inch plane grating 
ruled by Dr. J. A. Anderson, of Johns Hopkins University, was obtained 
about the New Year, which gives great concentration of light in the 
first order at one side, over 50% of the light incident upon the grating 
being diffracted into this order. A spectrograph has been designed, 
and is now being constructed in the Observatory workshop, to enable 
this grating to be used in stellar spectroscopy, and it is hoped that 
valuable results may be obtained. 
The work on the solar rotation which as stated in the last report 
was definitely arranged for at the Mt. Wilson meeting of the Inter- 
national Union for Co-operation in Solar Research in 1910, has been 
actively prosecuted during the year. A large number of rotation 
plates were obtained and three series, two in the region allotted to the 
Dominion Observatory at 15600 and one in the general region at 4250, 
have been measured and reduced. The rotational values are about 2% 
lower than those obtained by Adams in 1906-7 and 1908, but whether 
this is due to a real change in the rate or to some instrumental or per- 
sonal cause is not yet determinable. It may be stated that some very 
curious and unexplainable differences in measures of the same plates 
