Young, Thomas, physicist, born in Somersetshire, of Quaker parents; studied medicine at home and abroad; renounced Quakerism, and began practice in London in 1800; was next year appointed professor of Natural Philosophy in the Royal Institution, 1802; made Secretary of the Royal Society, and was afterwards nominated for other important appointments; his principal work is a “Course of Lectures on Natural Philosophy and the Mechanical Arts,” published in 1807, in which he propounded the undulatory theory of light, and the principle of the interference of rays; the hieroglyphic inscriptions of Egypt occupied much of his attention, and he is credited with having anticipated Champollion in discovering the key to them (1773‒1829).
Definition taken from The Nuttall Encyclopædia, edited by the Reverend James Wood (1907)
Young, Robert * Young Men's Christian Association