The Stewart Observatory
Louis Beaufort Stewart, O.L.S., D.T.S., (1861-1937), a giant of early Canadian engineering, was the professor of surveying, geodesy and practical astronomy in the Department of Civil Engineering from 1901 till 1931. He was highly regarded by his colleagues and well liked by all his students.
This geodetic observatory was built in 1908 to support those programs. Laid out by Stewart himself, it was made with masonry from the old Toronto magnetic and meteorological observatory, which was demolished in 1907. Being similar in appearance, this structure thus serves also as a memorial to that famous and important institution. In 1953 this building was turned over to the Students' Administrative Council for their use.
Plaque via Alan L. Brown's site Toronto Plaques. Full page here.