CLVI ROYAL SOCIETY OF CANADA 



two stations on the southern boundary of British Columbia, one on or 

 near the southern boundary of Manitoba in the neighbourhood of Lake 

 of the Woods, and three in Ontario on the Minnesota border. For the 

 latter use three stations were observed in Ontario, eight in Quebec, eight 

 in New Brunswick and two in Nova Scotia, making twenty-seven alto- 

 gether. The longitudes of the two most westerly stations were deter- 

 mined by telegraphic exchange of signals with Seattle, a point of known 

 longitude. The other stations were determined by direct exchange with 

 the Observatory. 



ASTEOPIIYSICS. 



Stellar spectroscopy for the determination of the radial velocities 

 of stars has continued to form the principal work in Astrophysics. The 

 elements of the orbits of five binary systems have thus been determined. 

 There are twelve others under observation. 



The instrumental equipment for this work has been increased by 

 the addition of a single prism spectroscope designed by Mr. Plaskett, 

 and constructed, except the optical parts, entirely in the Observatory 

 workshop. A principal aim in the design was the avoiding of flexure. 

 In this full success has been achieved. The maximum flexure produced 

 by a revolution of the instrument through 180° is not measurable, being 

 even not certainly visible under high magnification. 



Various investigations having in view the improvement of the in- 

 struments have been made, as for example, enquiry as to the best type 

 of camera objectives for spectrographs, as to the effect of different slit 

 widths on the errors of measurement of the radial velocity, and tests of 

 the optical performance of the lenses of the instruments. 



The coelostat house has been completed, and the instruments 

 mounted, but little work has yet been done towards spectroscopic in- 

 vestigations of the sun, it having been found that the grating of the 

 spectrograph was imperfect, on account of which a very thorough in- 

 vestigation of it has had to be made. The tests applied have indicated 

 that good definition can be secured by covering a part of the grating. 



Other work in this division has been micrometric measurements of 

 double stars, comet photographs, observations of occultations of stars by 

 the moon, and solar photography. This work, as well as all the other 

 astronomical work, greatly suffered from the dense smoke from the forest 

 fires which prevailed during a great part of last summer. 



Geophysics. 



The Bosch seismograph has been in constant operation during the 

 year, and has given very good records 



