Modern instruments and methods of calculation : a handbook of the Napier Tercentenary Exhibition (1914)
Horsburg, E. M. (Ellice Martin), Napier Tercentenary Exhibition (1914 : Edinburgh, Scotalnd) · London : G. Bell · leaf 333
Fig. i.—Model of the Half-twist Surface. as the point of intersection moves along it. In the twist surfaces the generat-ing line is always at right angles to a lixed circle, and rotates about the tangentto the circle at the point of intersection, as the point of intersection movesround the circle.…
