"A lens is a transparent body the two refracting surfaces of which are curved, or one of which is curved and the other plane.(1) Double convex(2) Plano convex(3) Meniscus(4)Double concave(5) Plano concave(6) Concavo concave." -Avery 1895

Lens

"A lens is a transparent body the two refracting surfaces of which are curved, or one of which is curved…

"a, prism; b, plane glass; c, spherical lens; d, double-convex; e, plano-convex, f, double-concave; g, plano-concave; h, meniscus; i, concavo-convex lenses." -Comstock 1850

Lenses of Various Forms

"a, prism; b, plane glass; c, spherical lens; d, double-convex; e, plano-convex, f, double-concave;…

An illustration of the concave of a meniscus.

Concave of Meniscus

An illustration of the concave of a meniscus.

An illustration of the convex of a meniscus.

Convex of Meniscus

An illustration of the convex of a meniscus.