Stratford in Perth County, Ontario — Central Canada (North America)

Sir John Cunningham McLennan, 1867-1935

Photographed by Tim Boyd, July 18, 2025

1. Sir John Cunningham McLennan, 1867-1935 Marker

Inscription. An outstanding Canadian scientist, McLennan was born in Ingersoll and moved to this house in 1883. He attended the University of Toronto where he later became Head of the Physics Department. His research and publications brought international recognition to the University's physics laboratory, which bears his name. A leading advocate of close ties between science, industry and government, McLennan was instrumental in founding the Advisory Council on Industrial and Scientific Research, later the National Research Council. His work in England on the magnetic detection of submarines and the use of radium in the treatment of cancer, his explanation of the yellow-green light in the spectrum of the aurora borealis and his success in liquefying helium, contributed to his world-wide reputation. He was knighted in 1935.

Erected by Ontario Heritage Foundation.

Topics and series. This historical marker is listed in this topic list: Science & Medicine. In addition, it is included in the Canada, Ontario Heritage Trust series list. A significant historical year for this entry is 1883.

Location. 43° 22.514′ N, 80° 58.671′ W. Marker

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is in Stratford, Ontario, in Perth County. It can be reached from William Street. The marker is behind the McLennan house at 203 William Street, accessible on the Northshore Recreational Trail footpath on the north side of Victoria Lake, approximately 150 metres east of Waterloo Street North. Touch for map. Marker is at or near this postal address: 215 William Street, Stratford ON N5A 4Y3, Canada. Touch for directions.

Regionally, this marker is in the Huron-Perth-Waterloo-Wellington Area

and in Southwestern Ontario.

It is also in Central Canada.

Globally, it is in North America,

the Western Hemisphere,

the Western World,

and the Anglosphere.

Historically, it finds itself in what was once a British colony,

the Viceroyalty of New France,

the Haudenosaunee (Iroquois) Confederacy,

and Rupert’s Land.

Other nearby markers. At least 8 other markers are within walking distance of this marker: 203 William Street (within shouting distance of this marker); William Allman Memorial Arena (about 120 meters away, measured in a direct line); Swan Parade (about 120 meters away); R. Thomas Orr 1870-1957 (about 240 meters away);

Photographed by Tim Boyd, July 18, 2025

2. Sir John Cunningham McLennan, 1867-1935 Marker

The Bandshell (approx. 0.4 kilometers away); Stratford’s Furniture Industry (approx. 0.4 kilometers away); Knox Presbyterian Church (approx. 0.4 kilometers away); The Queen’s Inn (approx. half a kilometer away). Touch for a list and map of all markers in Stratford.

Also see . . . McLennan, Sir John Cunningham (Dictionary Of Canadian Biography).

Throughout his long tenure at the University of Toronto, Sir John Cunningham McLennan had been a major contributor to physical-science research. His interests paralleled the rapidly developing fields of early-20th-century physics, from radioactivity to spectroscopy and low-temperature physics; in total he published more than 240 papers. He gained international recognition as Canada’s most prominent physicist. Upon learning of his death, Lord Rutherford, a long-time friend, wrote in the London Times that McLennan was “the acknowledged leader of science in Canada.”

(Submitted on July 21, 2025, by Tim Boyd of Hamilton, Ontario.)

Entrance to the Northshore Recreation Trail from Waterloo Street North image. Click for full size.

Photographed by Tim Boyd, July 18, 2025

3. Entrance to the Northshore Recreation Trail from Waterloo Street North

The marker is approx. 150 metres east of this point

Sir John Cunningham McLennan ca 1930 image. Click for full size.

4. Sir John Cunningham McLennan ca 1930

Source: Library of Congress (public domain)

The Sir John Cunningham McLennan House image. Click for full size.

Photographed by Tim Boyd, July 18, 2025

5. The Sir John Cunningham McLennan House

Credits. This page was last revised on July 21, 2025. It was originally submitted on July 21, 2025, by Tim Boyd of Hamilton, Ontario. This page has been viewed 83 times since then and 19 times this year. Photos: 1, 2, 3, 4, 5. submitted on July 21, 2025, by Tim Boyd of Hamilton, Ontario. • Andrew Ruppenstein was the editor who published this page.