sentences:  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.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.Sir John Henry Lefroy, a pioneer in the study of terrestrial magnetism served as director of the magnetic observatory from 1842 to 1853; In 1960, the Ontario Heritage Foundation, Ministry of Citizenship and Culture erected a Provincial Military Plaque in his honour on the University of Toronto campus.