In the sum­mer of 1868, the British Asso­ci­a­tion for the Advance­ment of Sci­ence held its annu­al meet­ing in the town of Nor­wich, 90 miles north­east of Lon­don. At that meet­ing, Thomas Hen­ry Hux­ley, one of the great­est nat­ur­al his­to­ri­ans of his day and a cham­pi­on of Dar­win’s new the­o­ry of evo­lu­tion, deliv­ered a talk enti­tled “On a Piece of Chalk.” His audi­ence was the ordi­nary work­ing­men of the town.