nappen.

1879 G. A. Wentworth Elem. Plane & Solid Geom. vii. 338 A conical surface generated by an indefinite straight line consists of two portions, called Nappes, one the Lower, the other the Upper Nappe.

1894 Amer. Math. Monthly 1 261 In an ellipse, the cutting plane falls short of the other nappe of the cone.

1904 Trans. Amer. Math. Soc. 5 432 We inquire whether there are any surfaces for which the characteristic lines on the sheets of the evolute correspond. Let the focal nappes be referred to the conjugate system corresponding to the lines of curvature of the surface.

1931 Ann. Math. 32 114 The part of the neighborhood of (v) which lies in the plane u₃ = 0 will go over into a nappe of (14).

1953 Amer. Math. Monthly 60 603 On the surfaces of negative curvature..admitting a finite number of expanding infinite nappes, the geodesics behave in a way which presents an interesting philosophical problem.

1991 C. B. Boyer & U. C. Merzbach Hist. Math. (ed. 2) ix. 147 The erroneous impression..that the words ellipse, parabola, and hyperbola were adopted by Apollonius to indicate that the cutting plane fell short of, ran along with, or ran into the second nappe of the cone.

1844 Edinb. New Philos. Jrnl. 37 323 A sheet of such water-logged stone, or of permanently wet sand, is called by the French geologists a ‘Nappe d'Eau’; it is not a sheet of pure water, but a bed or sheet of sand or stones, whose interstices are filled with water, subject to the laws of hydrostatic pressure.]

1887 Philos. Trans. 1886 (Royal Soc.) 177 384 In a later paper, Savart showed that the jet vibrations are preserved in the ‘nappe’, or thin sheet of liquid formed when the jet strikes normally on a small surface.

1892 Marichal & Trantwine tr. M. Bazin in Proc. Engineers' Club Philadelphia 9 231 We now proceed to study the form of the sheet of water passing over the weir. [translator's note] For want of a convenient English equivalent, we shall designate this sheet by its very appropriate French name, the nappe, a name applied primarily to a table-cloth, the form of which..is well imitated by the sheet of water passing over the weir.

1923 F. C. Lea Hydraulics 81 The sheet of water flowing over a weir or through a notch is generally called the vein, sheet, or nappe.

1945 W. P. Creager et al. Engin. for Dams II. xi. 357 If the area below the lower nappe is filled with masonry, the shape of the sheet and the discharge will not be changed appreciably.

1966 F. M. Henderson Open Channel Flow vi. 177 If the nappe is contained within parallel walls downstream of the weir, it may well enclose the air between itself, walls, and floor.

1991 Public Wks. Oct. 76/3 The insert pipe was then lowered into the water nappe, and a new head reading was taken.

1922 Q. Jrnl. Geol. Soc. 78 87 In deciding upon the basal limit to be assigned to any particular nappe, one generally chooses some prominent thrustplane; failing this, one is entitled to select the axial plane of some recumbent anticline or syncline, according to local convenience.

1944 A. Holmes Princ. Physical Geol. vi. 81 Tear faults are commonly developed in nappes, where they naturally arise if one part of a nappe has been driven forward further than the adjoining parts.

1970 D. L. Linton & F. Moseley in Cambr. Anc. Hist. (ed. 3) I. i. i. 15 The Gulf of Oman, in which a series of ‘nappes’ or horizontally displaced rock sheets have been successively driven from north-east to south-west.

1997 Proc. National Acad. Sci. U.S.A. 94 6003/2 The upper tillite, the Blaskrans, occurs in thrust sheets of the Naukluft Nappe Complex.