[Thomas Young, Physician at St George's Hospital, London, and authority on optics.] Corrected Autograph Notes for a lecture on optics.

A whole section of Young's entry in the Oxford Dictionary of National Biography is devoted to Young's activities in the field of optics, a topic concerning which he gave the Royal Society Bakerian lecture for 1800, entitled ‘The mechanism of the eye’. This MS. 4pp., 12mo. Bifolium. In fair condition, on aged and worn paper, with slight damp staining at foot. The first page is headed '(3)', and amended to '(2)'. It begins '<...> light reflected goes in straight lines | A Ray of light falling on a bason [sic] of water is bent or refracted from its course hence put a straight Cane in water it appears crooked. The ray is bent towards a perpendicular drawn from the point.' He moves to 'rays passing thro glass', before turning to how pictures are formed on the eye ('Philosophers have perplexd themselves much about this.') He discusses the question with reference to Albrecht von Haller (1708-1777), William Porterfield (1696-1771) and William Cheselden (1688-1752). The final page begins: 'How do we see an object single with the Eyes, it is from an instinct & I say [...?]: that children use their eyes at the same time without any reasoning of it, Cheselden's patient who he [couched?] did not see double we can judge of one sound tho we have two Ears; By the two eyes we judge better of distances hence a person with one eye can't snuff a candle so well, nor pour out a cup of tea or put a Stick thro a ring - A gentleman in shooting at a Crow by shutting the Eye it disappeard, the fact was he had lost the power of the othr. eye gradually tho he was not sensible of it'. The last page concludes with a discussion of squinting. Note: the hand of Young has benn identified by comparison with other (signed) items.