Hyperboloid and Asymptotic Cone, string surface model, 1872.

This is one of a large set of ruled surface models made by Fabre de Lagrange of Paris in 1872, following designs introduced in the early 19th century. They illustrate surfaces which can be traced out in space by the movement of a straight line. This model shows a hyperboloid of one sheet with its asymptotic cone. The tangent plane to the cone is also drawn.