the exterior surface of a convex, that is, gibbous and globular thing; in opposition to concavity, or the inner surface, which is hollow or depressed.

A convex lens is either convex on both sides, called a convexo-convex; or it is plain on one side and convex on the other, called a plano-convex; or concave on one side and convex on the other, called a concavo-convex, or concavo-convex; as the one or the other surface prevails, that is, as this or that is a portion of a smaller sphere. All convex lenses inflect the rays of light in their passage, or send them out from their convex surface converging, so that they concur in a point or focus. Hence all convex lenses magnify, or represent the images larger than their objects; and they do this the more as they are portions of smaller spheres.