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Illustration of a compass with one leg at point A on the line segment and the other at Point B.

Compass and Line

Illustration of a compass with one leg at point A on the line segment and the other at Point B.

Illustration of a compass with one leg at point O on the line segment and the other at Point M.

Compass and Line

Illustration of a compass with one leg at point O on the line segment and the other at Point M.

Of the hyacinth family (Hyacinthaceae), the Star-of-Bethlehem or Ornithogalum umbellatum.

Star of Bethlehem Hyacinth

Of the hyacinth family (Hyacinthaceae), the Star-of-Bethlehem or Ornithogalum umbellatum.

Of the amaryllis family (Amaryllidaceae), star grass or Hypoxis hirsuta.

Star Grass

Of the amaryllis family (Amaryllidaceae), star grass or Hypoxis hirsuta.

Illustration showing that the sum of all the angles about a point equals 360°.

360° Sum of Angles

Illustration showing that the sum of all the angles about a point equals 360°.

"Look through the rear-sight notch at the bull's-eye or mark and bring the top of the front sight on a line with the top of and in the center of the rear-sight notch and aligned upon the point of aim." -Moss, 1914

Normal Sight

"Look through the rear-sight notch at the bull's-eye or mark and bring the top of the front sight on…

"Look through the peep hole at the bull's-eye or mark and bring the top of the front sight to the center of the aperture and aligned upon the point of aim." -Moss, 1914

Peep Sight

"Look through the peep hole at the bull's-eye or mark and bring the top of the front sight to the center…

The echinoderm, the crinoid or feather-star.

Crinoid

The echinoderm, the crinoid or feather-star.

"Starfish. I. Ventral surface; t.f., tube-feet extended; a.g., the ambulacral groove with the tube-feet retracted; m., the mouth. II. Dorsal surface, showing the position of the madrepore (M.); the two adjacent arms form the bivium." -Thomson, 1916

Starfish

"Starfish. I. Ventral surface; t.f., tube-feet extended; a.g., the ambulacral groove with the tube-feet…

"Diagrammatic cross-section of starfish arm. n., Radial nerve; b.v., radial blood vessel according to Ludwig, septum in pseud-haemal vessel according to others; w.v., radial water vessel; am., ampulla; t.f., tube-foot; p.c., a pyloric caecum cut across; s.p., a calcareous spine; g., a skin-gill; lac., spaces in the wall; go., ova in ovary; a.o., ambulacral ossicle." -Thomson, 1916

Starfish Arm

"Diagrammatic cross-section of starfish arm. n., Radial nerve; b.v., radial blood vessel according to…

"Ventral surface of disc of an Ophiuroid (Ophiothrix fragilis). g., Openings of genital pockets or bursae; m., mouth; v., ventral plates of arms; sp., spines of arms; tf., tube-feet--at the right side these are represented as retracted; o., the opening through which they are protruded; p., plates around mouth bearing the so-called teeth; one of these plates is perforated, and functions as the madreporite." -Thomson, 1916

Ophiuroid

"Ventral surface of disc of an Ophiuroid (Ophiothrix fragilis). g., Openings of genital pockets or bursae;…

"Diagram showing arrangement of the nervous matter in Starfish. c, ganglionated ring about the mouth; o, mouth; r.n., radial nerve in each arm." -Galloway, 1915

Starfish Nervous System

"Diagram showing arrangement of the nervous matter in Starfish. c, ganglionated ring about the mouth;…

"Transverse section of the arm of a Starfish near the disc. Diagrammatic. Lettering as in preceding figure. a.r., ambulacral rafter (ossicle); ov., ovary, containing ova." -Galloway, 1915

Starfish Arm Section

"Transverse section of the arm of a Starfish near the disc. Diagrammatic. Lettering as in preceding…

Illustration of the construction used to create a perpendicular to a straight line at a given point.

Construction Of A Perpendicular To A Straight Line

Illustration of the construction used to create a perpendicular to a straight line at a given point.

Illustration of the construction used to create a perpendicular to a straight line from a given point not on the line.

Construction Of A Perpendicular To A Straight Line

Illustration of the construction used to create a perpendicular to a straight line from a given point…

Illustration used to prove the corollary that "From a point outside a line there exists only one perpendicular to the line."

Perpendicular to Line Corollary

Illustration used to prove the corollary that "From a point outside a line there exists only one perpendicular…

Illustration of triangle ABC with BE extended through the triangle at point D. Segment AB is equal to segment BD.

Segments Labeled In A Triangle

Illustration of triangle ABC with BE extended through the triangle at point D. Segment AB is equal to…

"Acuminate.--Having an open or awl-shaped point." -Newman, 1850

Acuminate

"Acuminate.--Having an open or awl-shaped point." -Newman, 1850

"Decurrent.--When leaves run down the stem to a point considerably below the place where they diverge from it." -Newman, 1850

Decurrent Leaf

"Decurrent.--When leaves run down the stem to a point considerably below the place where they diverge…

"Aculeus.--A prickle or sharp point, from the bark." -Newman, 1850

Aculeus

"Aculeus.--A prickle or sharp point, from the bark." -Newman, 1850

"Asterias rubens. Digestive system. an, anus; card. st, cardiac division of the stomach; int. caec, intestinal caeca; madr, madreporite; ply. caec, pyloric caeca; pyl. st, pyloric division of the stomach." -Parker, 1900

Common Starfish

"Asterias rubens. Digestive system. an, anus; card. st, cardiac division of the stomach; int. caec,…

"Ambulacral system of a starfish. a, ampullae; ap, Polian vesicles; c, circular canal; m, madreporite; m', madreporic canal; p, tube-feet; r, radial vessels; r', branches to ampullae." -Parker, 1900

Ambulacral System

"Ambulacral system of a starfish. a, ampullae; ap, Polian vesicles; c, circular canal; m, madreporite;…

"Ophioglypha lacertosa. A, outline, of the natural size; B, central disc, dorsal view; C, the disc, ventral view showing the mouth and genital fissures." -Parker, 1900

O. Lacertosa

"Ophioglypha lacertosa. A, outline, of the natural size; B, central disc, dorsal view; C, the disc,…

"A, lateral view of skull of rattlesnake (Crotalus). B. O, basi-occipital; B. S, basi-sphenoid; E. O, exoccipital; F. O, fossa ovalis; La, conjoined lacrymal and pre-fontal; L. f, articulation between lacrymal and frontal; Mn, mandible; Mx, maxilla; Na, nasal; Pl, palatine; Pmx, pre-maxilla; P. Sph, pre-sphenoid; Pt, pterygoid; Qu, quadrate; Sq, squamosal; II. V, foramina of exit of the second and fifth cranial nerves. B, transverse section at point lettered B in Fig. .A; T, trabeculae." -Parker, 1900

Rattlesnake Skull

"A, lateral view of skull of rattlesnake (Crotalus). B. O, basi-occipital; B. S, basi-sphenoid; E. O,…

Of the Primrose family (Primulaceae), the shooting star (Dodecatheon Meadia).

Shooting Star

Of the Primrose family (Primulaceae), the shooting star (Dodecatheon Meadia).

Of the Composite family (Compositae), the tall blazing star (Liatris scariosa).

Tall Blazing Star

Of the Composite family (Compositae), the tall blazing star (Liatris scariosa).

Of the mud plantain family (Heteranthera), the water stargrass (Heteranthera dubia).

Water Stargrass

Of the mud plantain family (Heteranthera), the water stargrass (Heteranthera dubia).

Bone points and bone needles. Crafted during the Reindeer age.

Reindeer age articles, Bone points and needles

Bone points and bone needles. Crafted during the Reindeer age.

"Lengthwise section through root-tip of Indian corn. w, root-cap; i, younger part of cap; z, dead cells separating from cap; s, growing point; o, epidermis; p', intermediate layer between epidermis and central cylinder; p, central cylinder; d, layer from which the root-cap originates." -Bergen, 1896

Corn Root Tip

"Lengthwise section through root-tip of Indian corn. w, root-cap; i, younger part of cap; z, dead cells…

"Tips of leaves. a, acuminate or taper-pointed; b, acute; c, obtuse; d, truncate; e, retuse; f, emarginate or notched; g (end leaflet), obcordate; h, cuspidate, - the point sharp and rigid; i, mucronate, - the point merely a prolongation of the midrib." -Bergen, 1896

Leaf Tips

"Tips of leaves. a, acuminate or taper-pointed; b, acute; c, obtuse; d, truncate; e, retuse; f, emarginate…

Tar is made from the turpentine by the smothered burning of the wood. When burning the wood, it is placed in a pile resembling a cone with the point cut off.

Manufacturing of Turpentine

Tar is made from the turpentine by the smothered burning of the wood. When burning the wood, it is placed…

" The most singular of all the star fishes is the splendid Astrophyton. Its center is not unlike the gorgeous appearance of a Chinese wheel, but what a curious tie of twisting and twining tentacles." -Lupton

Singular Star Fish

" The most singular of all the star fishes is the splendid Astrophyton. Its center is not unlike the…

An illustration showing the construction used to erect a perpendicular from a point to a line. "With C as a center, draw the dotted circle arc so that it cuts the line at A and B. With A and B as centers, draw the dotted cross arcs at D with equal radii. Draw the required perpendicular through C and crossing D."

Construction Of A Perpendicular

An illustration showing the construction used to erect a perpendicular from a point to a line. "With…

An illustration showing the construction used to erect a perpendicular at the end of a line. "With the point D as a center at a distance from the line, and with AD as radius, draw the dotted circle arc so that it cuts the line at E through E and D, draw the diameter EC: then join C and A, which will be the required perpendicular."

Construction Of A Perpendicular

An illustration showing the construction used to erect a perpendicular at the end of a line. "With the…

An illustration showing the construction used to divide an angle into two equal parts when the lines do not extend to a meeting point. "Draw the lined CD and CE parallel, and at equal distances from the lines AB and FG. With C as a center, draw the dotted arc BG; and with B and G as centers, draw the cross arcs H. Join CD, which divides the angle into the required equal parts."

Construction Of A Divided Angle

An illustration showing the construction used to divide an angle into two equal parts when the lines…

An illustration showing how to construct a tangent to a circle through a given point in a circumference. "Through a given point A and center C, draw the line BC. With A as a center, draw the circle arcs B and C; with B and C as centers, draw the cross arcs D and E; then join D and E, which is the required tangent."

Construction Of Tangent To Circle

An illustration showing how to construct a tangent to a circle through a given point in a circumference.…

An illustration showing how to construct a tangent to a circle through a given point outside of a circumference. "Join A and C, and upon AC as a diameter draw the half circle ABC, which cuts the given circle at B. Join A and B, which is the required tangent."

Construction Of Tangent To Circle

An illustration showing how to construct a tangent to a circle through a given point outside of a circumference.…

An illustration showing how to construct a tangent circle to a circle with a given radius. "Through the given point C, draw the diameter AC extended beyond D: from C set off the given radius R to D; then D is the center of the required circle, which tangents the given circle at C."

Construction Of Circle Tangent To Circle

An illustration showing how to construct a tangent circle to a circle with a given radius. "Through…

"The Proteus anguinus attains a length of about 1 foot. The body is smooth, naked, and eel-like, the legs four in number, small and weak, the forefeet three-toed, the hinder four-toed, and in addition to permanent external gills, it possesses lungs in the form of slender tubes. From its inhabiting places devoid light the power f vision is unnecessary and in point of fact its eyes are rudimentary and covered by the skin." -Marshall

Proteus Anguinus

"The Proteus anguinus attains a length of about 1 foot. The body is smooth, naked, and eel-like, the…

An illustration showing how to construct the center and radius of a circle that will tangent a given circle. "Through the given point C, draw the tangent GF; bisect the angle FGE; then o is the center of the required circle that will tangent AB at C, and the line DE."

Construction Of A Center And Radius Of A Circle That Will Tangent A Given Circle

An illustration showing how to construct the center and radius of a circle that will tangent a given…

An illustration showing how to construct the center and radius of a circle that will tangent a given circle and line. "Through the given point C, draw the line EF at right angles to AB; set off from C the radius r of the given circle. Join G and F. With G and F as centers draw the arc crosses m and n. Join mn, and where it crosses the line EF is the center of the required circle."

Construction Of A Center And Radius Of A Circle That Will Tangent A Given Circle And Line

An illustration showing how to construct the center and radius of a circle that will tangent a given…

An illustration showing how to construct two circles that tangent themselves and two given lines. "Draw the center line AB between the given lines; assume D to be the tangenting point of the circles; draw DC at right angles to AB. With C as center and CD as radius, draw the circle EDF. From E, draw Em at right angles to EF; and from F draw Fm at right angles to FE; then m and n are the centers for the required circles."

Construction Of Two Circles That Tangent Themselves and 2 Given Lines

An illustration showing how to construct two circles that tangent themselves and two given lines. "Draw…

An illustration showing how to construct a circle that tangents two given lines inclined to one another with the one tangenting point being given. "Draw the center line GF. From E, draw EF at right angles to AB; then F is the center of the circle required.

Construction Of A Circle That Tangents 2 Given Lines

An illustration showing how to construct a circle that tangents two given lines inclined to one another…

An illustration showing how to construct a circle that tangents two given lines and goes through a given point c on the line FC, which bisects the angle of the lines. "Through C draw AB at right angles to CF; bisect the angles DAB and EBA, and the crossing on CF is the center of the required circle."

Construction Of A Circle That Tangents 2 Given Lines And Goes Through A Given Point

An illustration showing how to construct a circle that tangents two given lines and goes through a given…

An illustration showing how to construct a circle arc without recourse to its center, but its chord AB and height h being given. "With the chord as radius, and A and B as centers, draw the dotted circle arcs AC and BD. Through the point O draw the lines AOo and BOo. Make the arcs Co=Ao and Do=Bo. Divide these arcs into any desired number of equal parts, and number them as shown on the illustration. Join A and B with the divisions, and the crossings of equal numbers are points in the circle arc."

Construction Of A Circle Arc

An illustration showing how to construct a circle arc without recourse to its center, but its chord…

An illustration showing how to construct an isometric ellipse by compass and six circle arcs. "Divide OA and OB each into three equal parts; draw the quadrant AC. From C, draw the line Cc through the point 1. Through the points 2 draw de at an angle of 45° with the major axis. Then 2 is the center for the ends of the ellipse; e is the center for the arc dc; and C is the center for the arc cf."

Construction Of An Isometric Ellipse

An illustration showing how to construct an isometric ellipse by compass and six circle arcs. "Divide…

An illustration showing how to construct a hyperbola by plotting. "Having given the transverse axis BC, vertexes Aa, and foci ff'. Set off any desired number of parts on the axis below the focus, and number them 1,2,3,4,,5,etc. Take the distance a1 as radius, and, with f' as center, strike the cross 1 with f'1=a1. With the distance A1, and the focus f as center, strike the cross 1 with the radius F1=A1, and the cross 1 is a point in the hyperbola."

Construction Of A Hyperbola

An illustration showing how to construct a hyperbola by plotting. "Having given the transverse axis…

The Starry Ray is so called for having a number of spines on its upper surface rising from rayed or star like bases; it reaches a length of 30 inches.

Starry Ray

The Starry Ray is so called for having a number of spines on its upper surface rising from rayed or…

An illustration showing how to construct an ellipse. "With a as a center, draw two concentric circles with diameters equal to the long and short axes of the desired ellipse. Draw from o any number of radii, A, B, etc. Draw a line Bb' parallel to n and bb' parallel to m, then b is a point in the desired ellipse.

Construction Of An Ellipse

An illustration showing how to construct an ellipse. "With a as a center, draw two concentric circles…

An illustration showing how to construct an ellipse. Given the two axes, set off half the long axis from c to ff, which will be the two focuses in the ellipse. Divide the long axis into any number of parts, say a to be a division point. Take Aa as radius and f as center and describe a circle arc about b, take aB as radius and f as center describe another circle arc about b, then the intersection b is a point in the ellipse, and so the whole ellipse can be constructed."

Construction Of An Ellipse

An illustration showing how to construct an ellipse. Given the two axes, set off half the long axis…

An illustration showing how to construct a cycloid. "The circumference C=3.14D. Divide the rolling circle and base line C into a number of equal parts, draw through the division point the ordinates and abscissas, make aa' = 1d, bb' = 2'e, cc = 3f, then ab' and c' are points in the cycloid. In the Epicycloid and Hypocycloid the abscissas are circles and the ordinates are radii to one common center."

Construction Of A Cycloid

An illustration showing how to construct a cycloid. "The circumference C=3.14D. Divide the rolling circle…

An illustration showing how to construct a parabola. "Given the vertex A, axis x, and a point P. Draw AB at right angle to x, and BP parallel to x, divide AB and BP into an equal number of equal parts. From the vertex A draw lines to the divisions on BP, from the divisions on AB draw the ordinates parallel to x, the corresponding intersections are points in the parabola."

Construction Of A Parabola

An illustration showing how to construct a parabola. "Given the vertex A, axis x, and a point P. Draw…

An illustration showing how to construct a parabola. "Given the axis of ordinate B, and vertex A. Take A as a center and describe a semicircle from B which gives the focus of the parabola at f. Draw any ordinate y at right angle to the abscissa Ax, take a as radius and the focus f as a center, then intersect the ordinate y, by a circle-arc in P which will be a point in the parabola. In the same manner the whole Parabola is constructed."

Construction Of A Parabola

An illustration showing how to construct a parabola. "Given the axis of ordinate B, and vertex A. Take…

This table wheel would be used to practice the six tables. The teacher would rapidly point to the surrounding numbers and the students would enter. This can be done for addition or multiplication tables.

Table Wheel

This table wheel would be used to practice the six tables. The teacher would rapidly point to the surrounding…

Illustration showing two component forces ab and ac acting upon point a. The result is the vector ad (the diagonal of the parallelogram).

Vector Addition

Illustration showing two component forces ab and ac acting upon point a. The result is the vector ad…

The board of trade sign for 1/8 cent.

1/8 Cent

The board of trade sign for 1/8 cent.

A safety-valve, in which a weight is employed. Here a is the valve, b b the boiler, c c the valve-seat, usually, like the valve itself, made of gunmetal, d the lever turning upon a fixed center at e, and pressing upon the valve by a steel point f, a guide for the lever g a weight which may be shifted backwards and forwards according to the pressure desired.

Lever Safety-valve

A safety-valve, in which a weight is employed. Here a is the valve, b b the boiler, c c the valve-seat,…

A view of the labyrinth laid open. Labels: 1, The cochlea. 2, 3, Two channels that wind two and half turns around a central point (5). 7, The central portion of the labyrinth called the vestibule. 11, 12, 13, 14, 15, 16, 17, 18, The semicircular canals.

View of the Labyrinth Laid Open

A view of the labyrinth laid open. Labels: 1, The cochlea. 2, 3, Two channels that wind two and half…

A convex lens, bends the ray of light which pass through it, so that they meet at a point called a focus. The crystalline lens converges the rays of light which enter the eye, and brings them to a focus on the retina. The healthy lens has a power of changing its convexity so as to adapt itself to near and to distant objects.

The Use of the Crystalline Lens

A convex lens, bends the ray of light which pass through it, so that they meet at a point called a focus.…

Karyokinesis. Labels: a, ordinary nucleus of a columnar epithelial cell; B, C, the same nucleus in the stage of convolution; D, the wreath or rosette from; E, the aster, or single star; F, a nuclear spindle the Descemet's endothelium of the frog's cornea; G, H, I, diaster; K, two daughter nuclei.

Karyokinesis

Karyokinesis. Labels: a, ordinary nucleus of a columnar epithelial cell; B, C, the same nucleus in the…