Originally published by Cambridge University Press in 1900, A Treatise on the Theory of Screws is the definitive reference on screw theory. It gives a very complete geometrical treatment of the problems of small movements in rigid dynamics. In recent years the theory of screws has emerged as a novel mathematical resource for addressing complex engineering problems, with important applications to robotics, multibody dynamics, mechanical design, computational kinematics, and hybrid automatic control. The author, Sir Robert Stawell Ball, was born in Dublin in 1840 and studied at Trinity College, Dublin. When the Royal College of Science was founded in Dublin in 1867, Ball became the first professor of applied mathematics and mechanism. In 1874 he was appointed Royal Astronomer of Ireland, and in 1892 he assumed the Lowndean Chair of Astronomy and Geometry and the Directorship of the University Observatory at Cambridge, where he remained until his death in 1913.