"The spinal column below the twelfth dorsal vertebra at *A* has been removed, as well as the…

"1. fruit of Brexia madagascariensis; 2. a cross section of it; 3. a seed; 4. the same divided perpendicularly."…

"Gastrula of a Chalk-sponge (Olynthus). B, longitudinal section through the axis: g, primitive intestine;…

Illustration showing the definition of a circle as a conic section. The section of a right circular…

An illustration showing the intersection of a plane and a cone. The cone is intersected by a plane parallel…

Illustration showing a cone cut by a plane that is along the axis of symmetry.

The Basilica di Santa Maria del Fiore is the cathedral church (Duomo) of Florence, Italy, begun in 1296…

The Elisabeth Church in Marburg was built by the Order of the Teutonic Knights in honor of Elisabeth…

Illustration of half of an ellipse. "The ordinates of two corresponding points in an ellipse and its…

Illustration of half of an ellipse used to show that the area of an ellipse is equal to pi times a times…

Illustration showing the definition of an ellipse as a conic section. "The section of a right circular…

Illustration showing the definition of an ellipse as a conic section. "The section of a right circular…

Illustration showing the definition of an ellipse as a conic section. The section of a right circular…

An illustration showing the intersection of a plane and a cone. The cone is intersected by a plane neither…

Illustration showing that if one diameter is conjugate to a second, the second is conjugate to the first.

Illustration of half of an ellipse and its auxiliary circle used to construct an ellipse by points,…

Illustration showing the definition of an ellipse. "An ellipse is a curve which is the locus of a point…

Illustration of half of an ellipse. "If d denotes the abscissa of a point of an ellipse, r and r' its…

Illustration of an ellipse with foci F' and F, major axis A' to A, minor axis B' to B, and center O.

Illustration of half of an ellipse. "If through a point P of an ellipse a line is drawn bisecting the…

Illustration of half of an ellipse. The square of the ordinate of a point in an ellipse is to the product…

Illustration showing that tangents drawn at the ends of any diameter are parallel to each other.

Illustration of half of an ellipse. "The sum of the distances of any point from the foci of an ellipse…

Illustration of how to draw a tangent to an ellipse from an external point.

Illustration showing the tangents drawn at two corresponding points of an ellipse and its auxiliary…

"Section of Fortified Wall. (Interior on the left; exterior on the right.) a, a, is the abatis; b, b,…

"Gjers's Furnace Hoist. I. Section. II. Elevation. III. and IV. Plans." — The Encyclopedia Britannica,…

"Longitudinal section of a Hydra; *b*, bud which will form a young one; *ba*, base by…

Illustration showing the asymptotes of a hyperbola. The asymptotes will never meet the curve.

Illustration of a hyperbola and its auxiliary circle. "Any ordinate of a hyperbola is to the tangent…

Illustration showing the definition of an hyperbola as a conic section. "The section of a right circular…

Illustration showing the definition of an hyperbola as a conic section. A hyperbola is formed from a…

An illustration showing the intersection of a plane and a double cone. The cone is intersected by a…

Illustration showing how the a hyperbola is symmetrical with respect to its conjugate axis.

Illustration showing how a hyperbola con be constructed by points, having been given the foci and the…

Illustration showing the definition of an hyperbola. "An hyperbola may be described by the continuous…

Illustration of a hyperbola with distances to foci drawn. "The difference of the distances of any point…

Illustration of a hyperbola with a line bisecting the focal radii. "If through a point P of an hyperbola…

Illustration of a point on a hyperbola. "If d denotes the abscissa (x-coordinate) of a point of an hyperbola,…

Illustration showing how to draw a tangent to an hyperbola from a given point P on the convex side of…

The lines joining any point on a conic to the two foci are equally inclined to the tangent and normal…

"Lapidary's Dial. A, section; B, side elevation; a, a, jaws; b, ball; c, tube; d, dial; e, cement rod;…

The magic circle of circles, first developed by Benjamin Franklin, consists of eight annular rings and…

Section of the massif of Mont Dore, France, showing the succession of eruptions and the outline of the…

Section of frontal moraine on side of Warner Street, Glouchester, Massachusetts.

The modern Pearly Nautilus; the animal occupies the living chamber of the sectioned shell.

"It was in Central France, and mainly along the Loire, that the systematic development of vaulted church…

"Flowering Branch of Oleaster (Elaeagnus angustifolia). a, fruit; b, section of same." -Whitney, 1911