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dency of certain plant organs, as leaves, to assume special "sleeping" positions or make curvatures under the influence of darkness. It is well illustrated in the leaflets of clover and other leguminous plants.

reflected image on the convex surface of the cornea and lens of the eye, by which their curvature can be ascertained.

To touch closely, so as to have a common curvature at the point of contact. See Osculation, 2.

e Osculating circle of a curve, under Circle. -- Osculatory plane (to a curve of double curvature), a plane which passes through three successive points of the curve. -- Osculatory sphere (to a line of double curvature), a sphere passing through four consecutive points of the curve.

s (Opt.), spectacles having concavo-convex or convexo-concave lenses with a considerable curvature corresponding to that of the eye, to increase the distinctness of objects viewed obliquely.

tion of light to the movements of plants and their organs; the study of the phenomena of curvatures induced by the stimulus of light. --Pho`to*dy*nam"ic (#), Pho`to*dy*nam"ic*al (#), a.

a surface, any section of which by a like surface is a straight line; a surface without curvature.

Caries of the vertebræ, frequently resulting in curvature of the spine and paralysis of the lower extremities; -- so named from Percival Pott, an English surgeon. Pott's fracture, a fracture of the lower end of the fibula, with displacement of the tibia. Dunglison.

The surface of constant negative curvature generated by the revolution of a tractrix. This surface corresponds in non-Euclidian space to the sphere in ordinary space. An important property of the surface is that any figure drawn upon it can be displaced in any way without tearing it or altering in size any of its eleme…

s other end attached to a piece which it causes to move in a circular arc. -- Radius of curvature. See under Curvature.

Recurvation.

A lateral curvature of the spine.

ny line which passes through the optical center of a lens but not through the centers of curvature, or, in the case of a mirror, which passes through the center of curvature but not through the center of the mirror. -- Secondary battery. (Elec.) See under Battery, n., 4. -- Secondary circle (Geom. & Astron.), a great…

The longitudinal upward curvature of the deck, gunwale, and lines of a vessel, as when viewed from the side.

r frame. -- Skew bridge. See under Bridge, n. -- Skew curve (Geom.), a curve of double curvature, or a twisted curve. See Plane curve, under Curve. -- Skew gearing, or Skew bevel gearing (Mach.), toothed gearing, generally resembling bevel gearing, for connecting two shafts that are neither parallel nor intersecting…

An instrument for measuring the curvature of spherical surface, as of lenses for telescope, etc.

cted, it is called locked-jaw, or lickjaw, and it takes various names from the various incurvations of the body resulting from the spasm.

indefinitely small angle between two consecutive osculating planes of a curve of double curvature. -- Moment of torsion (Mech.) the moment of a pair of equal and opposite couples which tend to twist a body. -- Torsion balance (Physics.), an instrument for estimating very minute forces, as electric or magnetic attrac…

irally; subjected to torsion; hence, perverted. Twisted curve (Geom.), a curve of double curvature. See Plane curve, under Curve. -- Twisted surface (Geom.), a surface described by a straight line moving according to any law whatever, yet so that the consecutive positions of the line shall not be in one plane; a warpe…

A point of a surface at which the curvatures of the normal sections are all equal to each other. A sphere may be osculatory to the surface in every direction at an umbilicus. Called also umbilic.