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Illustration showing the construction of a golden rectangle. Beginning with a unit square, a line is then drawn from the midpoint of one side of the square to its opposite corner. Using that line, an arc is drawn that defines the length of the rectangle. Two quantities are considered to be in the golden ratio if (a+ b)/a = a/b which is represented by the Greek letter phi.

Construction Of A Golden Rectangle

Illustration showing the construction of a golden rectangle. Beginning with a unit square, a line is…

A section through the cochlea in the line of its axis.

The Cochlea of the Ear

A section through the cochlea in the line of its axis.

Leaves - simple; alternate, edge entire. Outline - long oval or long egg-shape. Apex - pointed. Base - pointed or rounded. Leaf - three to five inches long, thickish; dark and smooth, usually shining, above; below dull, with ribs curved and irregular and minutely downy. On the upper surface the ribs are quite indistinct, except as the lea is held toward the light when they appear almost transparent. In the same position the left is seen also to be edged with a slight delicate fringe (appearing in the dried leaf like a line of yellow light). Bark - of trunk dark and rough. Flowers - greenish-yellow and small, at the base of the leaf-stems. June. Fruit - about one inch in diameter, rounded, nearly stemless, orange-red when ripe, with about eight large flat seeds. After frost it is of very pleasant flavor, before, exceedingly "puckery." Found - from Connecticut southward to Florida and westward to Southeastern Iowa. General Information - A tree twenty to sixty feet high; sometimes, at the South, more than one hundred feet high. The wood is hard and close-grained; the bark tonic and astringent. From two Greek words meaning fruit of Jove.

Genus Diospyros, L. (Persimmon)

Leaves - simple; alternate, edge entire. Outline - long oval or long egg-shape. Apex - pointed. Base…

Leaves - Simple; indeterminate in position because of their closeness; arranged singly up and down the branchlets, at first radiating about equally on every side, afterward flattened into two ranks, as in the Hemlock. Leaf - one half to one inch long, narrow; apex blunt or notched; edge entire; flat, with a grooved line above and a corresponding raised line below; bright green above; silvery white below. Bark - smooth and unbroken (especially when young), and usually covered with "blisters." Cones - two to four inches long, one inch broad, erect, at the sides of the branchlets; violet-colored. Scales - thin and flat, broad and rounded. The thin bracts between the scales are tipped with a slender bristle. The cone falls apart when ripe. Found - from the far North through the Northern States to Pennsylvania, and along the Alleghany Mountains to the high peaks of West Virginia. Common northward in damp forests. General Information - A slender, evergreen tree, twenty to sixty feet high; pyramid-shaped, with regular horizontal branches; its wood is very light and soft. From the "blisters," which form under the bark of the trunk and branches, the valuable Canada balsam is obtained. The tree is short-lived, and therefore of less value in cultivation.

Genus Abies, Link. (Fir)

Leaves - Simple; indeterminate in position because of their closeness; arranged singly up and down the…

Leaves - simple; indeterminate in position because of their smallness and closeness. They are scale-like, somewhat egg-shape, overlapping each other, and closely pressed in four rows up and down the very flat branchlets. Each leaf has at its centre a raised gland, easily distinguished if held between the eye and the light. Bark - fibrous. The "spray" (formed from the flat branchlets) is itself flat and very delicate and of a dull green. Cones - about one fourth of an inch in diameter, round, variously placed, compact, purplish as they ripen; opening when ripe toward the centre line (i. e., not toward its base). Scales - fleshy, shield-shaped and apparently fastened near their centres, with the edge several-pointed, and with a sharp point or knob in the centre. Seeds - usually four to eight under each scale, oval, with wide wings at the sides. Found - in deep, cold swamps (filling them densely and exclusively), from Southern Maine along the coast to Florida, and along the Gulf coast to Mississippi. General Information - A tapering evergreen tree, thirty to seventy feet high, with light and durable wood, largely used in boat-building, for wooden-ware, shingles, etc.

Genus Chamaecyparis, Spach. (White Cedar)

Leaves - simple; indeterminate in position because of their smallness and closeness. They are scale-like,…

Parts of two hairs embedded in their follicles. Labels: a, the skin, which is seen to dip down and line the follicle; b, the subcutaneous tissue; c, the muscles of the hair follicle, which by their contraction can erect the hair; o, sebaceous gland.

Hairs and their Follicles

Parts of two hairs embedded in their follicles. Labels: a, the skin, which is seen to dip down and line…

An erasing shield of thin metal is convenient in erasing desired shapes.

Straight Line Erasing Shield

An erasing shield of thin metal is convenient in erasing desired shapes.

Section of the head showing the greater scythe, the horizontal apophysis of the dura mater between the brain and the cerebellum and other parts under the middle line of the head.

Head, Section of

Section of the head showing the greater scythe, the horizontal apophysis of the dura mater between the…

For drawing straight lines and curves that are not arcs of circles, the ruling pen is used. The distance between the pen points, which regulates the width of line to be drawn, is adjusted by the thumb screw, and the blades are given a slight curvature so that there will be a cavity for ink when the points are close together.

Ruling Pen

For drawing straight lines and curves that are not arcs of circles, the ruling pen is used. The distance…

Circle pattern exercise: Draw diagonals A C and D B, and with the T-square draw the line E H. Now mark off on E H distances of 1.4 inch, and with H as a center describe, by means of the compasses, circles having radii respectively 2 inches, 1.5 inches, 1 inch, 0.75 inch, 0.5 inch, and .25 inch. Similarly with H as a center and a radius of 1.75 inch and 1.25 inches respectively raw the arcs F G and I J and K L and M N, being careful to end the arcs in the diagonals.

Circle Exercise

Circle pattern exercise: Draw diagonals A C and D B, and with the T-square draw the line E H. Now mark…

All lines in a mechanical drawing are made with the aid of an instrument. Horizontal lines are drawn with the upper edge of the T-square blade as a guide.

Drawing a Horizontal Line

All lines in a mechanical drawing are made with the aid of an instrument. Horizontal lines are drawn…

Vertical lines are drawn by using a triangle held against the T-square.

Drawing a Vertical Line

Vertical lines are drawn by using a triangle held against the T-square.

Parallel lines are drawn by using a triangle in combination with a T-square. To draw a line parallel to the one given, place a triangle against the T-square and move them together until the hypotenuse of the triangle matches the line. Hold the T-square firmly and slide the triangle in the direction of the arrow until the desired position of the parallel line is reached.

Drawing Parallel Lines Exercise

Parallel lines are drawn by using a triangle in combination with a T-square. To draw a line parallel…

Lines perpendicular to each other may be drawn by using a triangle in combination with the T-square. To draw a line perpendicular to a given line place a triangle against the T-square and move them together until the hypotenuse of the triangle matches the line. Turn the triangle on its right angled corner until the perpendicular line can be drawn on the hypotenuse of the triangle.

Drawing Perpendicular Lines Exercise

Lines perpendicular to each other may be drawn by using a triangle in combination with the T-square.…

A serious membrane. These line all closed cavities, or sac, of the body, and are reflected over the organs contained in them. They form a shut sac, completely excluding the air.

Serous Membrane

A serious membrane. These line all closed cavities, or sac, of the body, and are reflected over the…

A portion of the stomach, showing its internal surface or mucous coat. Mucous membranes line various cavities of the body, which are exposed to the air.

Mucous Membrane

A portion of the stomach, showing its internal surface or mucous coat. Mucous membranes line various…

Do not hold the pen over the drawing while filing. Keep the blades parallel to the direction of the line

Pen Positioning

Do not hold the pen over the drawing while filing. Keep the blades parallel to the direction of the…

Always draw a circle in one stroke, inclining the compass in the direction of the line and rolling the handle between the thumb and finger.

Inking a Circle

Always draw a circle in one stroke, inclining the compass in the direction of the line and rolling the…

The word "Monday" as clothes on a line drying in the sun.

Monday Banner

The word "Monday" as clothes on a line drying in the sun.

The line of characters and their actions in order for the pig to go over the stile.

Old Woman and Animals

The line of characters and their actions in order for the pig to go over the stile.

"a, a', impressions of the muscles; p, pallial line; s, bend occupied by the siphon; h, hinge; c, t, t', teeth." -Cooper, 1887

Clamshell

"a, a', impressions of the muscles; p, pallial line; s, bend occupied by the siphon; h, hinge; c, t,…

"Diagram illustrating the position of the groundwater surface (the dotted line) in a region of undulating topography." -Salisbury, 1919

Groundwater Position

"Diagram illustrating the position of the groundwater surface (the dotted line) in a region of undulating…

The diagram shows how to determine North by sun and plumb line.

Determining North

The diagram shows how to determine North by sun and plumb line.

"A, diagram showing relative position of the guard cells in cross section in the open and closed positions; the heavier line indicates the open position." -Stevens, 1916

Stoma Guard Cells

"A, diagram showing relative position of the guard cells in cross section in the open and closed positions;…

"Diagram to show the relation of the food-conducting tissues of the leaf to those of the stem; and in the stem the relation of these tissues of one year to those of preceding years. The dotted line between phloem and xylem stands for the cambium. The figures at the bottom of the diagram indicate the age in years of the zones of tissues in phloem and xylem." -Stevens, 1916

Food Tissues

"Diagram to show the relation of the food-conducting tissues of the leaf to those of the stem; and in…

"Where the sea bottom has a very gentle slope, the waves break at some distance from the shore and the sand they carry is deposited, forming a barrier beach (B) along the line of greatest disturbance. The strip of water inclosed between the land and the barrier beach is called a lagoon (L)." -Dryer, 1901

Barrier Beach

"Where the sea bottom has a very gentle slope, the waves break at some distance from the shore and the…

"The line AB represents the surface of a water wave whose length is ai, moving in the direction of the long arrow. Suppose the wave length to be divided into eight equal parts, ab, bc, etc. If the water were still, the particles 1, 2, 3, etc., would lie directly above the points a, b, c, etc., but each particle is moving in a circular path in the direction shown by the curved arrows." -Dryer, 1901

Wave Movement

"The line AB represents the surface of a water wave whose length is ai, moving in the direction of the…

"BA is the ray of light passing through a rare medium (as, for instance, air); and upon its entrance into a denser medium (as, for instance, water) the ray will be deflected from the direction of its path BA, and will take the course AE. If the line CD is perpendicular to the dividing surface between the two media, then BAC is the angle of incidence and DAE is the angle of refraction." -Waldo, 1896

Atmospheric Optics

"BA is the ray of light passing through a rare medium (as, for instance, air); and upon its entrance…

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.

A, the malleus, or mallet, with its long handle running down, to touch with its delicate extremity the membrane of the drum. B, is the incus, or anvil, nicely fitted to the mallet, and showing C, the orbicular bone placed between its termination, and D, the stirrup. The line a,b, represents the center of motion of the malleus, and c,d, the center of motion of the incus. Now this chain of bones acts on the principle of a long level, as a small motion at one end of a long pole serve to move it through a wide space at the other.

Bones of the Ear

A, the malleus, or mallet, with its long handle running down, to touch with its delicate extremity the…

Illustration showing two parallel vertical lines cut by a perpendicular line and a transversal. Congruent line segments are marked.

Parallel Lines Cut By a Perpendicular And Transversal

Illustration showing two parallel vertical lines cut by a perpendicular line and a transversal. Congruent…

Illustration used to show how to construct an equilateral triangle, with a given line as a side.

Construction Of Equilateral Triangle

Illustration used to show how to construct an equilateral triangle, with a given line as a side.

"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…

"Trenches may be classified into fire trenches, cover trenches, and communication trenches, the first named being occupied by the firing line, the second by the supports, and the last by troops passing between the first and second." -Moss, 1914

Trenches

"Trenches may be classified into fire trenches, cover trenches, and communication trenches, the first…

The image represents the horizontal clock face system. The bottom is the firing line and the numbers of the clock references the position of other objects.

Horizontal Clock Face System

The image represents the horizontal clock face system. The bottom is the firing line and the numbers…

"Simple orthoclase crystal showing cleavage lines and the position of the twinning plane in a Carlsbad twin." -Johannsen, 1908

Orthoclase Crystal

"Simple orthoclase crystal showing cleavage lines and the position of the twinning plane in a Carlsbad…

"Cross-section through Ascaris. d.n., Dorsal nerve; n.c., non-contractile portion of muscle cells; c., cuticle; e., epidermis; l.l., lateral line; e.v., excretory vessel; m., contractile portion of muscle cells; v.n., ventral nerve; ov., ovary; ut., uterus; g., gut." -Thomson, 1916

Ascaris

"Cross-section through Ascaris. d.n., Dorsal nerve; n.c., non-contractile portion of muscle cells; c.,…

"Ventral aspect of male cockroach with the wings extended. An imaginary median line has been inserted. A., antennae; E., eye; P.T., prothorax; W1, first pair of wings; W2, second pair of wings; C., cercus; St., style; Co., coxa; Tr., trochanter; F., femur; Ti., tibia; Ta., tarsus." -Thomson, 1916

Cockroach

"Ventral aspect of male cockroach with the wings extended. An imaginary median line has been inserted.…

"The fresh-water mussel...the inside of the shell (left valve)...u., The umbo; L., the ligament; c.t., lateral teeth; a.a., anterior adductor mark; a.r., mark of protractor of the foot; p.l., pallial line; p.a., posterior adductor mark; p.r., mark of posterior retractor of the foot; A., anterior (the blunter end); P., posterior." -Thomson, 1916

Freshwater Mussel

"The fresh-water mussel...the inside of the shell (left valve)...u., The umbo; L., the ligament; c.t.,…

"The fresh-water mussel...the outside of the shell (right valve)...u., The umbo; L., the ligament; l.g., a line of growth; A., anterior (the blunter end); P., posterior; V., ventral." -Thomson, 1916

Freshwater Mussel

"The fresh-water mussel...the outside of the shell (right valve)...u., The umbo; L., the ligament; l.g.,…

"External characters of a Teleostean--a carp (Cyprinus carpio). R., Dorsal unpaired fin; S., homocercal caudal fin; A., anal fin; B., B., pectoral and pelvic paired fins. Note also the lateral line and barbule." -Thomson, 1916

Carp

"External characters of a Teleostean--a carp (Cyprinus carpio). R., Dorsal unpaired fin; S., homocercal…

"Head region of Protopterus. sn.t., Sensory tubes; l.l., lateral line; e.br., external gills; pc.l., pectoral fin; op., operculum." -Thomson, 1916

African Lungfish Head

"Head region of Protopterus. sn.t., Sensory tubes; l.l., lateral line; e.br., external gills; pc.l.,…

"Side view of skull of Lacerta. px., Premaxilla; mx., maxilla; l., lachrymal; j., jugal; t.pa., transpalatine; epg., epipterygoid; pg., pterygoid; bpg., basipterygoid; b.o., basioccipital; q., quadrate; oc.c., occipital condyle; sq., squamosal; pr.o., pro-otic; pt.o., postorbital; st.1, st.2, supratemporals; ps., presphenoid (the optic nerve is seen issuing in front of the end of the reference line); p.e., mesethmoid; s.ob., supraorbitals; pf., prefrontal; n., nasal; ar., articular; ag., angular; sag., surangular; cr., coranary; d., dentary." -Thomson, 1916

Lizard Skull

"Side view of skull of Lacerta. px., Premaxilla; mx., maxilla; l., lachrymal; j., jugal; t.pa., transpalatine;…

"Side view of rabbit's skull. Pmx., Premaxilla; Na., nasal; Fr., frontal; Pa., parietal; Sq., squamosal; S.O., supraoccipital; Per., periotic; T., tympanic (the reference line points to the bony external auditory meatus, beneath it lies the inflated bulla); PO., paroccipital process." -Thomson, 1916

Rabbit Skull

"Side view of rabbit's skull. Pmx., Premaxilla; Na., nasal; Fr., frontal; Pa., parietal; Sq., squamosal;…

"Lower surface of dog's skull. o.c., Occipital condyle; B.O., basioccipital; T., tympanic bulla; m.c., postglenoid process behind fossa for condyle of mandible; B.S., basisphenoid; P.S., base of presphenoid; V., vomer; M.2, second molar; M.1, first molar; Pm. 1-4, premolars, the 4th the large carnassial; c., canine; I.1-3, incisors; Pmx., premaxilla; mx., maxilla; Pal., palatine; J., jugal; A.S., alisphenoid; Pt., pterygoid; Sq., squamosal (the reference line points to the glenoid fossa)." -Thomson, 1916

Dog Skull

"Lower surface of dog's skull. o.c., Occipital condyle; B.O., basioccipital; T., tympanic bulla; m.c.,…

View of the heart with its several chambers exposed and the vessels in connection with them. Labels: 1, the superior vena cava. 2, the inferior vena cava. 3. the chamber called the auricle. 4. the right ventricle. 5. the line marking the passage between the two chambers, and the points of attachment of one margin of the valve. 6. the septum between the two ventricles. 7. the pulmonary artery, arising from the right ventricle, and dividing at 8 into right and left, of the corresponding lungs. 9. the four pulmonary veins, bringing the blood from the lungs into 10, the left auricle. 11. the left ventricle. 12. the aorta, arising from the left ventricle, and passing down behind the heart, to distribute blood to every part of the system. Thus the blood moves in a double circle, one from the heart to the body, and from the body back to the heart, called the systemic circle; the other, from the heart to the lung, and from the lung back to the heart, called the pulmonic circle.

Heart and its Chambers

View of the heart with its several chambers exposed and the vessels in connection with them. Labels:…

"Sections of types Coelenterates (diagrammatic): 1 (longitudinal) and 2 (transverse) of a tubular hydroid; 3, Sea Anemone (longitudinal); 4, same (transverse, at the level of the upper dotted line); 5, same (transverse section of same at the level of the dotted line. The continuous line is ectoderm, the broken line, entoderm, and the stippled portion, mesenchyma. c.c., circular canal; g, gullet; g.v., gastro-vascular cavity; m, mouth; ma., manubrium; mes., mesentery; mes.1, directive mesentery; o, ostium; r.c., radial canal; t, tentacle; v, velum." -Galloway, 1915

Cnidaria

"Sections of types Coelenterates (diagrammatic): 1 (longitudinal) and 2 (transverse) of a tubular hydroid;…

Illustration of the construction used to make a perpendicular bisector of a straight line.

Construction Of A Perpendicular Bisector Of A Straight Line

Illustration of the construction used to make a perpendicular bisector of a straight line.

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 used to prove that "If two straight lines are parallel to a third straight line, they are parallel to each other."

Parallel Lines Theorem

Illustration used to prove that "If two straight lines are parallel to a third straight line, they are…

Illustration of two straight lines cut by a transversal. The 8 angles formed are labeled.

2 Lines Cut By A Transversal

Illustration of two straight lines cut by a transversal. The 8 angles formed are labeled.

Illustration used to prove the theorem, "If two straight lines are cut by a transversal making a pair of alternate interior angles equal, the lines are parallel."

Parallel Lines Cut By A Transversal Theorem

Illustration used to prove the theorem, "If two straight lines are cut by a transversal making a pair…

Illustration of two straight lines, m and n, cut by a transversal t.

2 Lines Cut By A Transversal

Illustration of two straight lines, m and n, cut by a transversal t.

Illustration of two straight lines, AB and CD, cut by a transversal EF.

2 Lines Cut By A Transversal

Illustration of two straight lines, AB and CD, cut by a transversal EF.

Illustration of the construction used to create a line parallel to a given line.

Construction Of A Parallel Line

Illustration of the construction used to create a line parallel to a given line.

Illustration used to prove the theorem, "If two parallel lines are cut by a transversal, the alternate interior angles are equal."

Parallel Lines Cut By A Transversal Theorem

Illustration used to prove the theorem, "If two parallel lines are cut by a transversal, the alternate…

Illustration used to prove the corollary that "Two lines perpendicular respectively to two intersecting lines also intersect."

Intersecting Lines Corollary

Illustration used to prove the corollary that "Two lines perpendicular respectively to two intersecting…