Fleming was a scientist and thinker. In 1849, he decided to establish an organization to communicate the results of work carried out by architects, surveyors and engineers: this was the Canadian Institute of Toronto, which became a well-known scientific society dedicated to the advancement of arts and sciences.
In 1852, the Institute began to publish a periodical, the Canadian Journal, to which Fleming was a frequent contributor. Fleming looked for support from his colleagues at the Institute, and from other British and American scientific associations, when in 1879, he made his proposal for universal time. Fleming was also a founding member of the Royal Society of Canada.
His strength lay in his capacity to establish strategic alliances to support his ideas. His friends included influential members of political, scientific and business circles such as Donald Smith of the Canadian Pacific, John A. Macdonald, Prime Minister of Canada, and Macdonald’s wife.