[Illustration: _Frontispiece_--BUILDING AND DOME FROM SOUTH] DEPARTMENT OF THE INTERIOR Hon. Charles Stewart Minister W. W. Cory, C.M.G. Deputy Minister The Dominion Astrophysical Observatory Victoria, B.C. A sketch of the development of astronomy in Canada and of the founding of this observatory. A description of the building and of the mechanical and optical details of the telescope. An account of the principal work of the institution. By J. S. Plaskett, F.R.S. Ottawa F. A. ACLAND, Printer to the King’s Most Excellent Majesty 1923 STAFF OF THE OBSERVATORY: Director J. S. Plaskett, B.A., D.Sc., F.R.S.C., F.R.S. Research Astronomer W. E. Harper, M.A. Astronomer Reynold K. Young, Ph.D., F.R.S.C. Astronomer H. H. Plaskett, B.A. Secretary Miss H. R. Keay Observing Assistant T. T. Hutchison, Esq. THE DOMINION ASTROPHYSICAL OBSERVATORY VICTORIA, B.C. By J. S. PLASKETT, Director. SECTION 1.--HISTORY AND CONSTRUCTION Introduction This description of the observatory, its equipment and work has been written by the director in response to a need, frequently expressed by the numerous visitors to the institution, of a non-technical account of the principles of the telescope and of the work of the institution. This account will commence by a short historical sketch of the beginnings of the undertaking followed by a description of the observatory and telescope and concluded by a resume of its work. Historical Sketch This observatory is a branch of the Department of the Interior of the Federal Government, the department which has charge of the administration of the western lands of the Dominion. In the colonization of these lands, one of the obvious first needs was a survey of the boundaries and subdivision into townships and sections. This need led to the organization of a surveys branch of the department and out of the necessity of accurate astronomical observations to delimit the boundaries and define the position of the base lines for subdivision work arose the astronomical branch. The first Chief Astronomer of Canada, the late Dr. W. F. King, was a man of sterling integrity and remarkable ability and to his genius must be ascribed in large degree the present development of astronomy in Canada. As Chief Astronomer and H. M. Commissioner of International Boundaries, he early realized the need of an observatory for an initial meridian, for housing and standardizing the instruments, and for some astronomical research. He was successful in having the fine Dominion Observatory erected on the Experimental Farm, Ottawa, in 1905 which housed the Astronomical Branch, the staff of the International Boundary Surveys and later the Geodetic Survey of Canada, of which he was the first superintendent.