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"A verticle section of one form of blast-furnace is represented [here]. the crucible (C) is the part of the furnace in which the molten matte and slag collect. The body of the furnace consists of two concentric shells (cs), made either of wrought iron or of steel, between which cold water (W) is caused to circulate to precent the inner shell becoming heated...Pipes called tuyeres (T) enter the furnace a short distance above the hearth...Above the body of the furnace extend the hood (H) and the stack (S). A door (D), used in charging the furnace, is placed in the hood." -Brownlee 1907

Blast-furnace

"A verticle section of one form of blast-furnace is represented [here]. the crucible (C) is the part…

Transverse section of compact tissue of humerus, magnified about 150 diameters. Three of the Haversian canals are seen, with their concentric rings faintly indicated; also the lacunae, with the canaliculi extending from them across the direction of the encircling lamellae, or concentric rings.

Bone Tissue of Humerus

Transverse section of compact tissue of humerus, magnified about 150 diameters. Three of the Haversian…

"Thus, if we suppose the conducting wire be placed in a vertical situation, as shown, and p, n, the current of positive electricity to be descending through it, from p to n, and if throught the point c in the wire in the plane NN be taken, perpendicular to p, n, that is in the present case a horiczontal plane, then if any number of circles be described in that plane, having c for thier common centre, the action of the current on the wire on upon the north pole of the magnet, will be to move it in a direction corresponding to the motion of the hands of a watch, having the dial towards the positive pole of the battery." -Comstock 1850

Circular Motion of the [Electric] Fluid

"Thus, if we suppose the conducting wire be placed in a vertical situation, as shown, and p, n, the…

"To find the center of gravity of any irregular plane figure, but of uniform thickness throughout, divide one of the parallel surfaces into triangles, parallelograms, circles, ellipses, etc., according to the shape of the figure; find the area and center of gravity of each part separately, and combine the center of gravity thus found in the same manner." —Hallock 1905

Center of Gravity of an Irregular Plane

"To find the center of gravity of any irregular plane figure, but of uniform thickness throughout, divide…

Cross section of pipe, 2 concentric circles

Cross Section of Pipe

Cross section of pipe, 2 concentric circles

2 circles that are similar figures

Similar Figures

2 circles that are similar figures

Illustration of concentric circles.

Concentric Circles

Illustration of concentric circles.

Illustration of polygon inscribed in circle. Or, circle circumscribed about the polygon.

Polygon Inscribed in Circle

Illustration of polygon inscribed in circle. Or, circle circumscribed about the polygon.

Illustration of point of tangency (line and circle).

Point of Tangency

Illustration of point of tangency (line and circle).

Illustration of polygon circumscribed about circle. Or, circle inscribed in the polygon.

Polygon Circumscribed About Circle

Illustration of polygon circumscribed about circle. Or, circle inscribed in the polygon.

Illustration of circle with inscribed angle and central angle.

Inscribed and Central Angles

Illustration of circle with inscribed angle and central angle.

Illustration of circle with arc and chord.

Arc and Chord in Circle

Illustration of circle with arc and chord.

Illustration of circle with inscribed angle 30 and central angle 60.

Inscribed and Central Angles 30 60

Illustration of circle with inscribed angle 30 and central angle 60.

Illustration of radius drawn to point of contact of a tangent.

Point of Tangency

Illustration of radius drawn to point of contact of a tangent.

Illustration of circle with segments labeled and arch.

Segments of Circle and Arch

Illustration of circle with segments labeled and arch.

Illustration of circle with parts drawn to show area.

Area of a Circle by parts

Illustration of circle with parts drawn to show area.

Illustration of concentric circles used to find area between two circles (ring).

Concentric Circles (Ring) Area

Illustration of concentric circles used to find area between two circles (ring).

Illustration of circles used to find area between two circles (ring).

Area of Circles and Rings

Illustration of circles used to find area between two circles (ring).

Illustration of circle with sector and segment used to find area.

Circle With Sector and Segment labeled

Illustration of circle with sector and segment used to find area.

Illustration of partial circle with sector and segment used to find area.

Circle With Sector and Segment labeled

Illustration of partial circle with sector and segment used to find area.

Illustration of circle with diameter and segment used to find area.

Circle With Diameter and Segment labeled

Illustration of circle with diameter and segment used to find area.

Illustration of circle with 8 inch diameter.

Circle With 8 inch Diameter

Illustration of circle with 8 inch diameter.

Illustration of circle with 6 inch diameter.

Circle With 6 inch Diameter

Illustration of circle with 6 inch diameter.

Illustration of circle with 10 inch diameter and square.

Circle With 10 inch Diameter and Steel Square

Illustration of circle with 10 inch diameter and square.

Illustration of box filled with pipes.

Circular Pipes in Box

Illustration of box filled with pipes.

Illustration of three circles enclosed in an equilateral triangle.

Circles Enclosed in Equilateral Triangle

Illustration of three circles enclosed in an equilateral triangle.

Illustration of circle with radius of 4000, and triangle with 45 degree angle enclosed.

Circles With Radius 4000 and Enclosed Triangle

Illustration of circle with radius of 4000, and triangle with 45 degree angle enclosed.

Illustration of circle with arc, chord, diameter and radius.

Parts of Circle

Illustration of circle with arc, chord, diameter and radius.

Illustration of circle with quadrant and 60 degree arc.

Quadrant of Circle With 60 degree Arc

Illustration of circle with quadrant and 60 degree arc.

Illustration of circle with perpendicular diameters.

Circle With Perpendicular Diameters

Illustration of circle with perpendicular diameters.

Illustration of large circle and square with 4 smaller circles inside.

Circles Inside of a Square

Illustration of large circle and square with 4 smaller circles inside.

Illustration of ring (small circle in larger concentric circle).

Ring Made of Concentric Circles

Illustration of ring (small circle in larger concentric circle).

Illustration of ring (small circle in larger concentric circle) with piece cut out.

Ring With Piece Cut Out

Illustration of ring (small circle in larger concentric circle) with piece cut out.

Illustration of ring (small circle in larger concentric circle) sprung into place.

Ring Sprung Into Place

Illustration of ring (small circle in larger concentric circle) sprung into place.

Illustration of triangle inscribed in circle. Or, circle circumscribed about triangle.

Triangle Inscribed in Circle

Illustration of triangle inscribed in circle. Or, circle circumscribed about triangle.

Illustration of pentagon inscribed in circle. Or, circle circumscribed about pentagon.

Pentagon Inscribed in Circle

Illustration of pentagon inscribed in circle. Or, circle circumscribed about pentagon.

Illustration of hexagon inscribed in circle. Or, circle circumscribed about hexagon.

Hexagon Inscribed in Circle

Illustration of hexagon inscribed in circle. Or, circle circumscribed about hexagon.

Illustration of Circle with radian shown.

Circle With Radian

Illustration of Circle with radian shown.

Circle divided into equal parts by concentric circles.

Dividing Circle into Equal Parts by Concentric

Circle divided into equal parts by concentric circles.

Illustration of circle with perpendicular diameters.

Circle With Perpendicular Diameters

Illustration of circle with perpendicular diameters.

Illustration of pentagon inscribed in circle. Or, circle circumscribed about pentagon. Construction lines shown.

Pentagon Inscribed in Circle by Construction

Illustration of pentagon inscribed in circle. Or, circle circumscribed about pentagon. Construction…

Illustration of regular hexagon and triangle inscribed in circle.

Hexagon Inscribed in Circle by Construction

Illustration of regular hexagon and triangle inscribed in circle.

Illustration of beginning of construction of a regular heptagon in a circle.

Construction of Regular Heptagon in a Circle

Illustration of beginning of construction of a regular heptagon in a circle.

Illustration of of construction of an arc when the chord and height of the segment are given.

Construction of Arc When Given the Chord and Height of the Segment

Illustration of of construction of an arc when the chord and height of the segment are given.

Illustration of of construction of a radius when given only a part of the circumference.

Construction of Radius When Given Only a Part of the Circumference

Illustration of of construction of a radius when given only a part of the circumference.

Illustration of of construction of a radius when given only a part of the circumference.

Construction of Radius When Given Only a Part of the Circumference

Illustration of of construction of a radius when given only a part of the circumference.

Right circular cylinder.

Right Circular Cylinder

Right circular cylinder.

Right circular cylinder inscribed in a pentagonal prism. Or, Pentagonal prism circumscribed about a cylinder.

Cylinder Inscribed in Pentagonal Prism

Right circular cylinder inscribed in a pentagonal prism. Or, Pentagonal prism circumscribed about a…

Right circular cylinder with diameter of 8 and height h.

Right Circular Cylinder

Right circular cylinder with diameter of 8 and height h.

Cross section of concrete conduit. The diagram can be used to find volume.

Cross Section of Concrete Conduit

Cross section of concrete conduit. The diagram can be used to find volume.

Cross section of Pullman car water tank. The diagram can be used to find volume.

Cross Section of Water Tank

Cross section of Pullman car water tank. The diagram can be used to find volume.

Cylindrical water tank with a height of 10 ft., thickness of 3 inches, and diameter of 3 feet. The diagram can be used to find volume.

Cylindrical Water Tank

Cylindrical water tank with a height of 10 ft., thickness of 3 inches, and diameter of 3 feet. The diagram…

Sheet metal blank for making a cylindrical box with a diameter of 1 inch and a height of 2 inches.

Cylindrical Box - Blank

Sheet metal blank for making a cylindrical box with a diameter of 1 inch and a height of 2 inches.

An illustration of a sphere showing diameter, arcs, and circles. A sphere is a solid bounded by a curved surface, every point of which is equally distant from a point within, called the center.

Sphere with arcs and circles labeled.

An illustration of a sphere showing diameter, arcs, and circles. A sphere is a solid bounded by a curved…

An illustration of a sphere showing diameter, arcs, and circles. A sphere is a solid bounded by a curved surface, every point of which is equally distant from a point within, called the center. This shows the zones of a sphere.

Sphere With Arcs, Circles, and Zones Labeled.

An illustration of a sphere showing diameter, arcs, and circles. A sphere is a solid bounded by a curved…

Right circular cylinder with a radius of 1 foot and a height/altitude of 2 feet.

Right Circular Cylinder With 1 ft. Radius and 2 ft. height.

Right circular cylinder with a radius of 1 foot and a height/altitude of 2 feet.

An illustration of a ring (circle within circle), with diameters of 3a-7 and 6a+9. Illustration could be used to calculate area.

Ring Made of Circles With Diameters 3a-7 and 6a+9

An illustration of a ring (circle within circle), with diameters of 3a-7 and 6a+9. Illustration could…

Illustration showing a circle inscribed in a regular pentagon. Or, a regular pentagon circumscribed about a circle.

Regular Pentagon With Circle Inscribed

Illustration showing a circle inscribed in a regular pentagon. Or, a regular pentagon circumscribed…

Lines for the detection of astigmatism. "The refracting surfaces of the eye acting together are equivalent in refracting power to a single, spherical surface of fairly short curvature. Frequently, however, the result is not the same as would be given by a perfect spherical surface, owing to inequalities in the curvature of the eye. In one direction the curvature may be greater than that at right angles to it. This tendency to a cylindrical form is called astigmatism. It interferes with the formation of perfect images and sometimes leads to serious eye strain in the effort to better the vision. Astigmatism may be detected by looking at black lines radiating from a point or at fine black concentric circles. Portions of the liens or circles appear gray and others black; the gray portions are out of focus. This defect is corrected by proper cylindrical glasses which equalize the curvature of the eye" — Newell, 1900

Detection of Astigmatism

Lines for the detection of astigmatism. "The refracting surfaces of the eye acting together are equivalent…

Illustrations of a circle with secant AD and line BC tangent to it.

Circle with Secant and Point of Tangency

Illustrations of a circle with secant AD and line BC tangent to it.