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s of the curve of the of the inner surface of an eggshell, in opposition to convex; as, a concave mirror; the concave arch of the sky.

Bowed in the form of an arch; -- called also arched.

Hollowness; concavity.

Concave on both sides; as, biconcave vertebræ.

Concave or hollow on both sides; double concave.

Convex on one side, and concave on the other. The curves of the convex and concave sides may be alike or may be different. See Meniscus.

Plane or flat on one side, and concave on the other; as, a plano-concave lens. See Lens.

Slightly concave. Owen.

sue. Achromatic lens (Opt.), a lens composed usually of two separate lenses, a convex and concave, of substances having different refractive and dispersive powers, as crown and flint glass, with the curvatures so adjusted that the chromatic aberration produced by the one is corrected by other, and light emerges from th…

Having both ends concave; biconcave; -- said of vertebræ.

nd with a very thin convex bottom. By sucking out a little air, the bottom springs into a concave form with a smart crack; and by breathing or blowing gently into the orifice, the bottom, with a like noise, springs into its former convex form.

tacking the bean, grape, melon, cotton, and other plants. In the case of the grape, brown concave spots are formed on the stem and fruit, and the disease is called bird's-eye rot.

A short wooden club having a deeply concave face, seldom used.

e), a projecting band of metal around the breech, connected with the body of the gun by a concave molding. H. L. Scott.

d materials, used in the arts or manufactures, as that used by glass grinders for forming concave glasses, by hatters for molding a hat into shape, etc.

s a small chambered cone, called the phragmocone, prolonged, on one side, into a delicate concave blade; the thunderstone. It is the internal shell of a cephalopod related to the sepia, and belonging to an extinct family. The belemnites are found in rocks of the Jurassic and Cretaceous ages. -- Bel*em*nit"ic, a.…

A concave vessel of various forms (often approximately hemisherical), to hold liquids, etc. Brought them food in bowls of basswood. Longfellow.

A concave tool used in grinding lenses or the speculums of telescopes. Knight.

mbranous part of which rises between the veins puckered elevations convex on one side and concave on the other.

lcined, to sublime the sulphur and arsenic from the pyrites. Weale. -- Burning mirror, a concave mirror, or a combination of plane mirrors, used for the same purpose as a burning glass.