Crookes is known as one of the most accomplished experimental physicists of his time. Among his discoveries are the element thallium as well as the cathode-ray tube.

The eldest child of sixteen born to a wealthy London businessman, Crookes was given ample opportunity to pursue his education. At age sixteen he entered the Royal College of Chemistry, studying under August Wilhelm von Hofmann (1818-1892) and eventually serving as his personal assistant. While a student Crookes became an accomplished organic chemist, publishing several papers; however, while attending a meeting at the Royal Institution he met the physicist Michael Faraday, who convinced him to switch his specialty to physics, and particularly to optics and spectroscopy.

After graduating from the Royal College of Chemistry in 1854, Crookes briefly held two academic positions, both of which he found very unsatisfying. After two years of lecturing he received a sizable inheritance from his father's...