Abstract: A device for removing material from the free surface of a contained body of liquid comprises a scoop supported from a fixed member by two links that carry a substantially horizontal arm on which the scoop is mounted so as to be rotatable about the axis of the arm. The connections of the links to the fixed member and to the arm are pivotal connections at the four corners of a quadrilateral. First actuating means pivots the link about its connection to the fixed member thereby to move the arm to and fro substantially in a horizontal plane. Second actuating means rotates the scoop about the axis of the arm.