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"It is found that the cord covering the curved surface is twice as long as the one covering the flat surface. So the area of the entire curved surface of a sphere is equal to the area of the surface of 4 circles like the one measured." -Foster, 1921

Area of Sphere

"It is found that the cord covering the curved surface is twice as long as the one covering the flat…

"The bases of the pyramids are considered as forming the surface of the sphere, while the altitude of the pyramids is the radius of the sphere." -Foster, 1921

Area of Sphere

"The bases of the pyramids are considered as forming the surface of the sphere, while the altitude of…

This Greek Aryballos is a small spherical shape with a narrow neck. It is used as a perfume vase.

Greek Aryballos

This Greek Aryballos is a small spherical shape with a narrow neck. It is used as a perfume vase.

This Antique bottle is made of red unpainted clay. It has a ring shape that is spherical and two handles.

Antique Bottle

This Antique bottle is made of red unpainted clay. It has a ring shape that is spherical and two handles.

This Egyptian bottle has a spherical bag-like body, almost disc shaped.

Egyptian Bottle

This Egyptian bottle has a spherical bag-like body, almost disc shaped.

"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;…

"The spherical aberration of a concave mirror is the deviation of some of the reflected light from the focus, as shown It arises from the curvature of the mirror, and causes an indistinctness or blurring of the image." -Avery 1895

Spherical Aberration of a Concave Mirror

"The spherical aberration of a concave mirror is the deviation of some of the reflected light from the…

"A convex mirror is generally a part of the other surface of a spherical shell. It increases the divergence, or decreases the convergence of light that falls upon it. The foci are virtual; the principal focus is midway between the center of the mirror and the center of curvature. The foci may be located and the images determined by processes closely similar to those used for concave mirrors, as illustrated." -Avery 1895

Convex Mirror

"A convex mirror is generally a part of the other surface of a spherical shell. It increases the divergence,…

"Spherical cell (resting stage of Amoeba) illustrating general or universal symmetry. Any plane passing through the center will divide it into two essentially equal portions." — Galloway

Spherical Cell

"Spherical cell (resting stage of Amoeba) illustrating general or universal symmetry. Any plane passing…