In 1938, the University of Toronto was the site of a major technological breakthrough.

It had been at least a decade since scientists had conceived of the possibility of "seeing the invisible." The human eye can only detect light of a narrow range of wavelengths: what we call "visible light." These waves are too crude to faithfully transmit the fine details of very small things. But rays of electrons behave as waves, and have a much shorter wavelength, and so, it was reasoned, could be used to "see the invisible."

Researchers in Europe had been pursuing this for years, but results were poor. E.F. Burton, the Chairman of the Physics Department at the University of Toronto, felt that Toronto had the potential to address the problem, so he assigned the task to two graduate students, James Hillier and Albert Prebus.

Hillier and Prebus together worked out the design of the microscope. They manufactured the parts themselves, in the machine shop of the Physics Department, working at night after the professional machinists had left. In four short (but intense!) months, their instrument was completed. The electron source is at the top, powered by a steady 45 000 Volts. Down the column, magnets focus the beam on the specimen. The whole chamber is kept in a vacuum, to maintain the electron beam. The resulting image was captured on a fluorescent screen or a photographic plate.

Where the light microscope could magnify objects up to 2500 times, the new electron microscope could magnify objects up to 40 000 times. But magnification was less important than resolution, the ability to distinguish elements that are very close together. An object can be magnified an enormous number of times, but without an increase in the resolution, no new information is provided. The new electron microscope achieved an unprecedented level of resolution. This was the real success.
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