On a Piece of Chalk was a 1868 lecture by Thomas Henry Huxley to the working men of Norwich during a meeting of the British Association for the Advancement of Science. It was published as an essay in Macmillan's Magazine in London later that year. The piece reconstructs the geological history of Britain from a simple piece of chalk and demonstrates science as "organized common sense". On a Piece of Chalk was republished by Scribner in 1967 with an introduction by Loren Eiseley and illustrations by Rudolf Freund.