Twist of deformation characteristics

Consider a regular surface in three-dimensional euclidean space subject to deformation. The difference between the torsion of a curve $L$ on the original surface and the torsion of the corresponding curve on the isometric deformed surface at points corresponding by the isometry is called the twist of $L$. A formula is introduced expressing the twist of characteristics of hyperbolic deformation of a surface in terms of its gaussian flexion.