On A Piece Of Chalk is a scientific essay written by Thomas Henry Huxley, a prominent biologist and naturalist in the late 19th century. The essay was originally delivered as a lecture to the working men of Norwich in 1868 and later published in the Fortnightly Review in the same year. The essay explores the geological history of the chalk cliffs of England and the microscopic organisms that make up the chalk itself. Huxley uses this as a starting...