Sir J.C. McLennan of Ingersoll, Ontario, was one of the leading experimentalists of his time. He began his studies at Toronto under James Loudon, became physics demonstrator in 1892, worked under J.J. Thompson at the Cavendish Laboratory at Cambridge in 1898-1899, and obtained the first Ph.D. in physics at Toronto in 1900. In 1905 he became chair of the Physical Laboratories, replacing James Loudon. He created an international reputation through his discoveries in radioactivity, low-temperature physics, and spectroscopy.

McLennan commissioned the Adam Hilger Company to make this Quartz Lummer plate for his studies of the Mercury Green Line. This plate was capable of showing the finer lines of the ultraviolet spectra. The original investigations derived from a desire to understand the green line in the spectrum of the Aurora Borealis. With this instrument, McLennan became the first to study these mysterious phenomena in the controlled setting of the laboratory. The physicist Raman wrote to McLennan, "Your work on the green line of the Aurora is one of the most sensational achievements in modern physics."


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