Hyperbolic paraboloid; a skew quadrilateral turning upon four hinges with parallel axes or pins; the lengths of the strings remain unaltered during deformation.
This is a mathematical surface model by Fabre de Lagrange (b. 1822). Mathematical surface models using threads were introduced as teaching aids in France after the Revolution. By the 1870s they were produced in significant numbers as they were considered the most useful models for teaching the Industrial Arts. The Museum has a large set of these models.