Toronto Magnetic and Meteorological Observatory
The original building was constructed in 1840 as part of a worldwide research project run by Edward Sabine to determine the cause of fluctuations in magnetic declination.
[1] When this project concluded in 1853, the observatory was greatly expanded by the Canadian government and served as the country's primary meteorological station and official timekeeper for over fifty years.
In 1836 the German explorer and naturalist Alexander von Humboldt wrote to Prince Augustus Frederick, Duke of Sussex, then President of the Royal Society, stating that a formal program was important to a nation with dominions spread across the globe.
[5] At the seventh meeting of the British Association in Liverpool in 1837, Sabine declared that "the magnetism of the earth cannot be counted less than one of the most important branches of the physical history of the planet we inhabit" and mapping its variations would be "regarded by our contemporaries and by posterity as a fitting enterprise of a maritime people; and a worthy achievement of a nation which has ever sought to rank foremost in every arduous undertaking".
[5] In 1839 the British Government and the Royal Society prepared four expeditions to build magnetic observation stations in Cape Town; St. Helena; Hobart, Tasmania and (eventually) Toronto, Ontario.
The team assigned to Canada originally planned to build their observatory on Saint Helen's Island off Montreal, but the local rocks proved to have a high magnetic influence, and the decision was made to move to Toronto instead.
The north end of the main building was connected to a small conical dome which contained a theodolite used to make astronomical measurements for the accurate determination of the local time.
Using the measurements from the Toronto and Hobart sites, Sabine noticed both short-term fluctuations in magnetic declination over a period of hours, and longer-term variations over months.
[11] With further data collected from the Toronto site, Sabine was able to demonstrate conclusively that the eleven-year sunspot cycle caused a similarly periodic variation in the Earth's magnetic field.
[10] He presented a third and conclusive paper on the topic in 1856, "On Periodical Laws Discoverable in the Mean Effects of the Larger Magnetic Disturbances", in which he singled out the Toronto site for particular praise.
Coincidentally, the Canadian government (having formed in 1867) was interested in taking part in the major international effort to accurately record the December 1882 Transit of Venus.
A large stone pillar was constructed inside the tower, raising the telescope to bring it closer to the dome and improve its field of view.
[16] A new magnetic observatory opened in 1898 in Agincourt, at that time largely empty fields,[1] (found on later maps on the north end of George Forfar farm east of Midland Avenue near Highway 401 or where Health Canada Protection Branch building resides today[18]) leaving the downtown campus location with its meteorological and solar observation duties.
[19] By 1907, new university buildings completely surrounded the observatory; dust from the construction clogged meteorological instruments, and at night electric lighting made astronomical work impossible.
The Meteorological Office decided to abandon the site and move to a new building at the north end of campus at 315 Bloor Street West, trading the original Observatory to the University in exchange for the new parcel of land.
