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"General View of Bara-Budur." — The Encyclopedia Britannica, 1893

Bara-Budur

"General View of Bara-Budur." — The Encyclopedia Britannica, 1893

"The common pump consists of a hollow tube, the lower part of which, descending into the water, is called the suction-pipe, and the upper part, b, the battel or cylinder; of a spout, s, at the top of the cylinder; of an air-tight priston, which works up and down in the cylinder; and of two valves, both opening upwards, one of which, g, is placed at the top of the suction-pipe, and the other, p, in the piston." — Wells, 1857

Pump

"The common pump consists of a hollow tube, the lower part of which, descending into the water, is called…

"In the forcing-pump atmospheric pressure plays but a small part. There is no valve in the piston c, but the water raised through the suction-pipe a, and the valve g, is forced by each depression of the piston up through the pipe e e, which is furnished with a valve to prevent the return of the fluid." — Wells, 1857

Forcing-Pump

"In the forcing-pump atmospheric pressure plays but a small part. There is no valve in the piston c,…

"The chain-pump consists of a tube or cylinder, the lower part of which is immersed in a well or reservoir, and the upper part enters the bottom of a cistern into which the water is to be raised. A chain is carried round a wheel at the top, and is furnished at equal distances with movable bottoms, which fit water-tight in the tube. As the wheel revolves, they successively enter the tube, and carry the water up before them, which is discharged into the cistern at the top of the tube." — Wells, 1857

Chain-Pump

"The chain-pump consists of a tube or cylinder, the lower part of which is immersed in a well or reservoir,…

"A form of an electrical machine. S being the glass cylinder turning on an axis, Y the conductor, F the rubber, A A supports." —Wells, 1857

Electrical Machine

"A form of an electrical machine. S being the glass cylinder turning on an axis, Y the conductor, F…

"Morse magnetic telegraph will be understood by reference to the accompanying diagram, which represents the construction and arrangement of this form of telegraph. F and E are pieces of soft iron surrounded by coils of wire, which are connected at a and b with wires proceeding from a galvanic battery. When a current is transmitted from a battery located one, two, or three hundred miles, as the case may be, it passes along the wires and into the coils surrounding the pieces of soft iron F and E, thereby converting them into magnets. Above these pieces of soft iron is a metallic bar or lever, A, supported on its center, and haing at one end the arm D, and at the other a small steel point, o. A ribbon of paper, p h, rolled on the cylinder B, is drawn slowly and steadily off by a train of clock-work, K, moved by the action of the weight P on the cord C. This clock-work gives motion to two metal rollers, G and H, between which the ribbon of paper passes, and which, turnin in opposite directions, draw the paper from the cylinder B. The roller H has a groove arond its circumference (not represented in the engraving) above which the paper passes. The steel point, r, or the lever, A, is also directly opposite this groove. The spring r prevents the point from resting upon the paper when the telegraph is not in operation." —Wells, 1857

Magnetic Telegraph

"Morse magnetic telegraph will be understood by reference to the accompanying diagram, which represents…

"A small porcelain cylinder ornamented with interlaced lotus flowers in intaglio, having a ring for suspension." — The Encyclopedia Britannica, 1910

Egyptian Charm

"A small porcelain cylinder ornamented with interlaced lotus flowers in intaglio, having a ring for…

"A section of part of a lace machine. E is the cylinder or beam upon which the lace is rolled as made, and upon which the ends of both warp and weft threads are fastened at starting. Beneath are w, w, w, a series of trays or beams, one above the other, containing the reels of the supplies of warp threads; c, c represent the slide bars for the passage of the bobbin b with its thread from k to k, the landing bars, one on each side of the rank of warp threads; s, t are the combs which take it in turns to press together the twistings as they are made. The combs are so regulated that they come away clear from the threads as soon as they have pressed them together and fall into positions ready to perform their pressing operations again." —The Encyclopedia Britannica, 1910

Lace Machine

"A section of part of a lace machine. E is the cylinder or beam upon which the lace is rolled as made,…

"Striking machines are now very generally used for the operation. These consist of a drum or cylinder having a parallel series of projecting knives, or plates of gun-metal, set angularly across its surface. Underneath the drum is a brass bed, fixed on a yielding cushion, which can be pressed up or eased by means of a foot lever, according as the leather operated on is thick or thin." —The Encyclopedia Britannica, 1910

Striking Machine

"Striking machines are now very generally used for the operation. These consist of a drum or cylinder…

"Catadioptric Holophote.—Part of the anterior hemisphere of rays is intercepted and at once parallelized by the lens L, whose principal focus (i.e., for parallel rays) is in the center of the flame, while the remainder is intercepted and made parallel by the paraboloid a, and thus the double agents in Fresnel's design are dispensed with. The rays of the posterior hemisphere are reflected by the spherical mirror b back again through the foxus, whence passing onwards one portion of them falls on the lens and the rest on the paraboloid, so as finally to emerge in union with and parallel to the front rays." —The Encyclopedia Britannica, 1910

Catadioptric Holophote

"Catadioptric Holophote.—Part of the anterior hemisphere of rays is intercepted and at once parallelized…

"Catadioptric Holophote.—Part of the anterior hemisphere of rays is intercepted and at once parallelized by the lens L, whose principal focus (i.e., for parallel rays) is in the center of the flame, while the remainder is intercepted and made parallel by the paraboloid a, and thus the double agents in Fresnel's design are dispensed with. The rays of the posterior hemisphere are reflected by the spherical mirror b back again through the foxus, whence passing onwards one portion of them falls on the lens and the rest on the paraboloid, so as finally to emerge in union with and parallel to the front rays." —The Encyclopedia Britannica, 1910

Catadioptric Holophote

"Catadioptric Holophote.—Part of the anterior hemisphere of rays is intercepted and at once parallelized…

"Professor Swan's Designs.—Among several ingenious arrangements and new forms of agents proposed by Professor Swan is the mode of sending rays from prisms through interstices left between other prisms placed in front, and also a form of agent which he termed the triesoptric prism, in which the rays would undergo two refractions and three reflexions. a are the front and b the triesoptric prisms. The two upper and lower prisms a are constructed of flint glass of high refractive power. It will be observed from the drawing that this ingenious arrangement is nevertheless open to objection, for cones of light of 30 degrees in front and of 65 degrees at the back are lost through the interstices." —The Encyclopedia Britannica, 1910

Swans Designs

"Professor Swan's Designs.—Among several ingenious arrangements and new forms of agents proposed by…

"Condensing Octant.—The central fixed apparatus bb with spherical mirror dd throws its rays directly over the angle of 45 degrees pgp, while the supplemental rays fall upon the straight condensing prisms p, each of which spreads the incident rays parallel to the corresponding rays in the central angle pgp. In this way the whole of the front hemisphere of rays is parallelized in the vertical plane and spread equally over the 45 degree in azimuth." —The Encyclopedia Britannica, 1910

Condensing Octant

"Condensing Octant.—The central fixed apparatus bb with spherical mirror dd throws its rays directly…

"Condensing Octant.—The central fixed apparatus bb with spherical mirror dd throws its rays directly over the angle of 45 degrees pgp, while the supplemental rays fall upon the straight condensing prisms p, each of which spreads the incident rays parallel to the corresponding rays in the central angle pgp. In this way the whole of the front hemisphere of rays is parallelized in the vertical plane and spread equally over the 45 degree in azimuth." —The Encyclopedia Britannica, 1910

Condensing Octant

"Condensing Octant.—The central fixed apparatus bb with spherical mirror dd throws its rays directly…

The front of a coin worth 100 copecks in Russia.

Ruble

The front of a coin worth 100 copecks in Russia.

"Courtney's Automatic Buoy. A, cylinder, 27 ft. 6 in. long; B, mooring shackle; C, rudder; D, buoy; E, diaphragm; F, ball valves; G, air inlet tubes; H, air (compressed) outlet tube to whistle; I, compressed air inlet to buoy; K, manhole; L, steps; N, whistle." —The Encyclopedia Britannica, 1910

Automatic Buoy

"Courtney's Automatic Buoy. A, cylinder, 27 ft. 6 in. long; B, mooring shackle; C, rudder; D, buoy;…

"aa is the mast, b tackle hook, c, c brass flanges for fixing parts of lantern together, e and g weather guards, h plate glass front of lantern, i shutter by which lamps are trimmed, k lamps, l silver reflector. Revolving catoptric apparatus was applied to floating lights in England, and M. Letourneau, in 1851, proposed to employ a number of sets of dioptric apparatus in one lantern." —The Encyclopedia Britannica, 1910

Floating Lights

"aa is the mast, b tackle hook, c, c brass flanges for fixing parts of lantern together, e and g weather…

The front of a common currency of India, Pakistan, and Sri Lanka.

Rupee

The front of a common currency of India, Pakistan, and Sri Lanka.

The front of a Rose Royal coin. It is a very rare English gold coin in the righ of King James 1. Worth thirty shillings.

Rose Ryal

The front of a Rose Royal coin. It is a very rare English gold coin in the righ of King James 1. Worth…

A horsemen's helmet viewed from the front.

Sallet

A horsemen's helmet viewed from the front.

"The simple outline of the atmospheric engine. Its mode of operation is as follows. Steam is admitted from the boiler into the cylinder, through the tube l, by means of a regulating cock, e, which is worked by a handle outside the boiler; the pressure of the atmosphere above the piston being thus balanced by the force of the steam beneath it, the extremity of the lever beam to whch the piston is attached is elevated by proportionate weights, w, attached to the pump-rod, and the piston is drawn to the top of the cylinder, the other extremity of the beam being depressed." —Comstock, 1850

Newcomens Engine

"The simple outline of the atmospheric engine. Its mode of operation is as follows. Steam is admitted…

"The first alteration to be noticed in the double-acting engine is that of the cylinder. To insure its double action, it is necessary to provide, at each end of the cylinder, a means of admission of steam from the boiler, and of escape for the steam to the condenser. Hence the double action, which means that the piston is both raised and depressed by the force of steam. For this purpose, a steam box is fixed to each end of the cylinder, communicating, in the one case with the upper, in the other with the lower, surface of the piston. B is the upper, and and B' the lower, steam box. Each of these boxes is furnished with two valves." —Comstock, 1850

Double-acting Cylinder

"The first alteration to be noticed in the double-acting engine is that of the cylinder. To insure its…

"The first alteration to be noticed in the double-acting engine is that of the cylinder. To insure its double action, it is necessary to provide, at each end of the cylinder, a means of admission of steam from the boiler, and of escape for the steam to the condenser. Hence the double action, which means that the piston is both raised and depressed by the force of steam. For this purpose, a steam box is fixed to each end of the cylinder, communicating, in the one case with the upper, in the other with the lower, surface of the piston. B is the upper, and and B' the lower, steam box. Each of these boxes is furnished with two valves." —Comstock, 1850

Double-acting Cylinder

"The first alteration to be noticed in the double-acting engine is that of the cylinder. To insure its…

"The following description of a section of Lord Rosse's telescope, though not so perfect as could be desired, is the best we could obtain. it exhibits a view of the inside of the eastern wall, with the tube, and machinery by which it is moved. A is the mason-work on the ground; B the universal joint, which allows the tube to turn in all directions; C the speculum in the tube; E the eye-piece through which the observer looks; F a pulley by which the tube is moved; H a chain attached to the pulley, and to the side of the tube; I, a chain running to K, the counterpoise; L, a lever connecting the chain M with the tube; Z another chain which passes from the upper part of the tube over a pulley at W, (not seen) and crosses to the opposite wall; X a railroad on which the speculum is drawn either to or from the tube. The dotted line H, shows the course of the weight R, as the tube rises or falls. The tube is moved from wall to wall by a ratchet wheel at R, which is turned by the lever O, on the circle N, the ends of which are fixed in the two walls." —Comstock, 1850

Telescope

"The following description of a section of Lord Rosse's telescope, though not so perfect as could be…

"The skeleton of the trunk and the limb arches seen from the front. C, clavicle; S, scapula; Oc, innominate bone attached to the side of the sacrum dorsally and meeting its fellow at the pubic symphysis in the ventral median line." —Martin, 1917

Skeletal Trunk

"The skeleton of the trunk and the limb arches seen from the front. C, clavicle; S, scapula; Oc, innominate…

"The superficial veins in front of the elbow-joint. B', tendon of biceps muscle; Bi, brachialis internus muscle; Pt, pronator teres muscle; 1, median nerve; 2, 3, 4, nerve-branches to the skin; B, brachial artery, with its small accompanying veins; cep, cephalic vein; bas, basilic vein; m', median vein; *, junction of a deep-lying vein with the cephalic." —Martin, 1917

Elbow-Joint

"The superficial veins in front of the elbow-joint. B', tendon of biceps muscle; Bi, brachialis internus…

"A self-acting screw-cutting lathe with double-geared headstock, of a type now well established, the arrangements for obtaining and varying this traversing motion may be observed. A steel leading screw runs along the front of the lathe bed, and with it the slide rest can be connected at pleasure. Two or more change wheels, properly proportioned as to the number of their teeth, connect the head of the screw with the hinder end of the mandrel." —The Encyclopedia Britannica, 1903

Screw-Cutting

"A self-acting screw-cutting lathe with double-geared headstock, of a type now well established, the…

Side view of the vertebra. 1: Body; 2: Processes; 3: Opening for spinal cord.

Vertebra

Side view of the vertebra. 1: Body; 2: Processes; 3: Opening for spinal cord.

Top view of the vertebra. 1: Body; 2: Processes; 3: Opening for spinal cord.

Vertebra

Top view of the vertebra. 1: Body; 2: Processes; 3: Opening for spinal cord.

Section of the femur. 1: External view; 2: Cellular portion at end; 3: Hollow in middle; 4: Thick shell of middle.

Femur

Section of the femur. 1: External view; 2: Cellular portion at end; 3: Hollow in middle; 4: Thick shell…

Longitudinal section of bone, a microscopic view. 1: Cells; 2: Canals; 3: Intercellular substance.

Bone Section

Longitudinal section of bone, a microscopic view. 1: Cells; 2: Canals; 3: Intercellular substance.

Cross-section of bone, a microscopic view. 1: Cells; 2: Canals; 3: Intercellular substance.

Bone Section

Cross-section of bone, a microscopic view. 1: Cells; 2: Canals; 3: Intercellular substance.

Vertical section of the skin, a microsopic view. 1: Cutis; 2: Cuticle in layers; 3: Papilla; 4: Nerves of the Papilla; 5: Opening of Perspiratory Gland; 6: Perspiratory Gland entire; 7: Vessels for secreting coloring matter; 8: Blood-vessels.

Skin

Vertical section of the skin, a microsopic view. 1: Cutis; 2: Cuticle in layers; 3: Papilla; 4: Nerves…

"A small cylinder of lime is heated to intense luminosity in the flame of a spirit lamp through which a jet of oxygen plays." —The Encyclopedia Britannica, 1903

Oxy-calcium Lamp

"A small cylinder of lime is heated to intense luminosity in the flame of a spirit lamp through which…

Full permanent set of teeth, seen in front.

Teeth

Full permanent set of teeth, seen in front.

External view of the Heart. 1: Right Auricle; 2: Left Auricle; 3: Right Ventricle; 4: Left Ventricle; 5: Systemic Veins; 6: Pulmonary Veins; 7: Aorta; 8: Pulmonary Artery; 9: Coronary Vein and Artery.

Heart

External view of the Heart. 1: Right Auricle; 2: Left Auricle; 3: Right Ventricle; 4: Left Ventricle;…

External view of the left side of Larynx. 1: Front portion of hyoid bone; 2: Upper edge of larynx; 3: Lower portion of larynx; 4: Second ring of trachea.

Larynx

External view of the left side of Larynx. 1: Front portion of hyoid bone; 2: Upper edge of larynx; 3:…

Cross section of the larynx above the vocal cords. 1: Right vocal cord. 2: Left vocal cord. 3: Cartilages to which the vocal cords are attached behind; 4: Front edge of the larynx.

Larynx

Cross section of the larynx above the vocal cords. 1: Right vocal cord. 2: Left vocal cord. 3: Cartilages…

"Side view of skull of Cape Jumping Hare. Pmx, premaxilla; Mx, maxilla; Ma, malar; Fr, frontal; L, lachrymal; Pa, parietal; Na, nasal; Sq, squamosal; Ty, tympanic; ExO, exoccipital; AS, alisphenoid; OS, orbito-sphenoid; Per, mastoid bulla." —The Encyclopedia Britannica, 1903

Cape Jumping Hare

"Side view of skull of Cape Jumping Hare. Pmx, premaxilla; Mx, maxilla; Ma, malar; Fr, frontal; L, lachrymal;…

"Front view of head of American Manatee, showing the eyes, nostrils, and mouth with the lobes of the upper lip divaricated." —The Encyclopedia Britannica, 1903

Manatee Face

"Front view of head of American Manatee, showing the eyes, nostrils, and mouth with the lobes of the…

"Front view of head of American Manatee, showing the eyes, nostrils, and mouth with the lip contracted." —The Encyclopedia Britannica, 1903

Manatee Face

"Front view of head of American Manatee, showing the eyes, nostrils, and mouth with the lip contracted."…

Babcock and Wilcox Water-tube Boiler, section at AB-front elevation

Babcock and Wilcox Water-tube Boiler

Babcock and Wilcox Water-tube Boiler, section at AB-front elevation

"AB is a strong metal tube, closed at the lower end, and carrying at the upper a bent pipe for admitting the compressed gas and a stop-cock R pierced with holes in a T form. DE and FG are two graduated glass tubes communicating at their lower ends by a narrow passage in the metal block to which they are hermetically fixed. DE and AB Also communicate at the upper ends by a passage in a metal piece attached bermetically to them. By the stop-cock R', having radial holes at right angles to each other, DE can communicate either with AB or with the atmosphere at O; and by the stop-cock R'' it can communicate either with FG or with the open air. The three tubes are surrounded by a cylinder MM' containing water to keep the temperature constant. The tube AB is filled with the compressed gas whose pressure is to be ascertained. Mercury is poured into FG till it fills DE and runs out at O." —The Encyclopedia Britannica, 1903

Regnaults Manometer

"AB is a strong metal tube, closed at the lower end, and carrying at the upper a bent pipe for admitting…

"The compressed air manometer consists of a strong graduated glass tube of uniform narrow bore, closed at the top and fixed hermetically into the neck of a wide iron cylinder. The tube contains dry air, and its lower end dips below the surface of mercury contained in the cylinder. Attached to the side of the cylinder is a tube A, with a stop-cock, to afford communication with the vessel the pressure in which is to be measured. When the manometer is attached to the vessel containing compressed gas the mercury rises in the glass tube till the pressure of the air confined in the tube plus the height of the mercury column above the level of the mercury in the cylinder is equal to the pressure on the surface of mercury in the cylinder." —The Encyclopedia Britannica, 1903

Compressed Air Manometer

"The compressed air manometer consists of a strong graduated glass tube of uniform narrow bore, closed…

"At sea the declination is generally observed by means of an azimuth compass invented by Kater. It consists of a magnet with a graduated compass card attached to it. At the side of the instrument opposite the eye there is a frame which projects upwards from the plane of the instrument in a nearly vertical direction, and this frame contains a wide rectangular slit cut into two parts by a wire extending lengthwise. The eye-piece is opposite this frame, and the observer is supposed to point the instrument in such a manner that the wire above mentioned shall bisect the sun's visible disk. There is a totally reflecting glass prism which throws into the eye-piece an image of the scale of the graduated card, so that the observer, having first bisected the sun's disk by the wire, must next read the division of the scale which is in the middle of the field of view." —The Encyclopedia Britannica, 1903

Azimuth Compass

"At sea the declination is generally observed by means of an azimuth compass invented by Kater. It consists…

"The original Merz micrometer of the Cape Observatory, made on Fraunhofer's model. S is the head of the micrometer screw proper, s that of the screw moving the slide to which the so-called "fixed web" is attached, s' that of a screw which moves the eye-piece E. C is the clamp and M the slow motion in position angle, L, L are tubes attached to a larger tube N; the latter fits loosely on a strong hollow cylinder which terminates in the screw V. By this screw the whole apparatus is attached to the telescope." —The Encyclopedia Britannica, 1903

Micrometer

"The original Merz micrometer of the Cape Observatory, made on Fraunhofer's model. S is the head of…

In this figure <em>BB</em> is the base line; <em>HH</em> the common horizontal or vanishing line; <em>C</em> the centre of view in that vanishing linel <em>LL</em> the vanishing line of the ascent; and <em>C1</em> the centre of view in that vanishing line.

Horizontal Line Diagram

In this figure BB is the base line; HH the common horizontal or vanishing line; C…

A diagram of the down-hill view to the eye.

Down-Hill View

A diagram of the down-hill view to the eye.

A cylinder

Cylinder

A cylinder

The perspective shown in this plate is parallel perspective; and the subject here intended to be represented is a flat and perfectly square surface, such as the floor of a room, a chess board, or any other such object. 1) The front edge of the given square; 2) One side of it receding to the vanishing point, which also is the point of sight; 3) The other side receding to the same point; 4) A line taken from one corner of the front edge, to the point of measuremen on the opposite side, and giving the perspective width or depth of the square at the intersection of the line 3; 5) A line drawn at the above intersection, and parallel to the front edge; this will give the back of the square. The lines 1, 2, 3, and 5 may then be strongly marked, and the figure will be thus completed. 6) This line is taken from the corner of the front edge to the opposite point of the measurement, showing how exactly either this line, o that marked 4, will give the perspective width of the square. It serves also to find the centre.

Parallel Perspective

The perspective shown in this plate is parallel perspective; and the subject here intended to be represented…

The perspective in this plate is "angular perspective," and the figure it represents is a flat square surface; its dimensions are supposed to be either twenty feet or twenty inches. 1) Two lines drawn from the nearest corner of theboard, to the horizontal line, and at a distance from each other equal to the thickness of the board; this fixes the vanishing point at 1. 2) A line drawn from the above vanishing point to the point of station. 3) A line taken at right angles to 2, from the point of station, and fixing on the horizontal line the position of the vanishing point 3. 4) Two lines drawn from the nearest corner of the board to the vanishing point 3, similarly to the previously drawn lines 1. 5) One point of measurement, obtained in the usual way, by the distance of 3 from the point of station. 6) The point of measurement. 7) The line of the geometrical scale, being a line drawn across the base of the nearest corner, and marked according to scale, twenty feet or twenty inches. 8,8) Lines taken from either end of the geometrical scale towards the point of measurement, but extending no farther than where they meet the lines 1,1, and 4,4. 9,10) Small perpendicular lines drawn at the above intersections, by which the width of the board is ascertained. 11) The side of the board opposite and really parallel to that marked 4, and therefore tending to the same vanishing point. 12) The back of the board, opposite and parallel to the front marked 1, and consequently tending to the same vanishing point. The lines 1,1; 4,4; 11 and 12, being strongly marked, the figure will be completed.

Angular Perspective

The perspective in this plate is "angular perspective," and the figure it represents is a flat square…

Two upright oblong figures are here represented in parallel perspective. They may be imagined to resemble the sides and fronts of houses, or their blank walls. One of the figures has two others attached to it of equal dimensions; and these additions might be similarly multiplied to any extent, by the numbers, 7, 8, 9 and 10, in the followig rules. 1) Lines forming to complete fronts of two separate and detached oblongs. 2) The geometrical scale at the base, marked twenty feet. 3) The ground lines of the fronts running to the vanishing point. 4) The top lines tending to vanishing point. 5) Lines from the geometrical scale, to the points of measurement, determining the perspective depths of the oblongs. 6) Perpendicular lines raised at the intersection of the lines 3 and 5, and giving the farthest upright corner lines of the oblongs. The two figures will thus be completed. The remaining lines inserted in the figure are intended to give two other oblongs (or rather their retiring sides) attached to the first, and supposed to be of the same dimensions. They are determined first by finding the centre 7 of the near corner line 1. From 7 a line is drawn to the vanishing point. A line marked 8 is then drawn from the near extremity of 1 through 6, where it is cut by 7; at its intersection with the bottom line 3, the perpendicular line 9 is raised, and another oblong front is completed. A line 10 is drawn, and determined as the line 8 was, from the top of 6, and by crossing the lines 7 and 3. The lines 13, 14, and 15, are inserted merely to show the inner side and back of the other oblong, as they would be seen were the object made of glass. Thus 13,13 are lines for the top and bottom of the back; formed by drawing them to the vanishing point; 14,14 are the top and bottom lines of the farthest side, found by straight lines being drawn from both ends of , until they meet 13,13; at which point of meeting the upright corner of the oblong are completed.

Parallel Perspective

Two upright oblong figures are here represented in parallel perspective. They may be imagined to resemble…

"A landscape is supposed to be viewed from the spot marked E; and that the spectator is desirous of representing on the plane of his paper a certain portion of the scene as seen by him fom this point. That portion constitutes his real picture. The distance of this picture,- or distance of the eye from the plane of the picture (which is the same thing), -means the distance intervening between the spectator's position, and that point on the ground directly in front of him, where the picture, which he is about to make, ought properly to commence. Upon the choice of a proper and judicious distance the beauty of his work will in a great measure depend. Suppose the landscape to be viewed from the point E, then that portion of the scene which the eye can easily take in, without moving the head, and without the slightest strain upon the optic nerve, will constitute the picture from that point. Now, under this condition the spectator will find that he does not distinctly see the ground immediately before him, but that he obtains a perfectly easy view of it only at some distance from his position at E. It is the space included between the point E (where he is placed), and the supposed point alluded to, and here marked S, that establishes the required distance of the picture, that is, the distance of the eye from the proposed picture. For instance, let S be that point on the ground immediately in front of the eye, and if through S a straight line be supposed to be drawn, perpendicular to the distance ES, this line will pass through and determine the foremost objects of the proposed picture, and therefore at this line the picture must commence."

Distance

"A landscape is supposed to be viewed from the spot marked E; and that the spectator is desirous of…

That an accurate notion of the vertical line may be obtained, the plane of the picture must be supposed to be perpendicular to the horizontal plane. If a straight line be drawn from the spectator's eye, perpendicular to this plane of the picture, that line will fall upon the plane at a point in the horizontal line directly opposite to the eye. This point, C, is called the centre of the picture, or centre of view. In reference to the eye of the spectator, every straight line perpendicular to the plane of the picture appears to converge towards this point or centre. The line which, drawn from the eye of the spectator, determines this centre C, is called the vertical line. It is a straight line through S, perpendicular to the horizontal line, and the base of the picture; and is represented by the line EC.

Vertical Line

That an accurate notion of the vertical line may be obtained, the plane of the picture must be supposed…

A side-view of the skull.

Skull

A side-view of the skull.

A front-view of the skull.

Skull

A front-view of the skull.

Nerve cell from the brain; <em>a</em>, processes by which it communicates with other cells near by; <em>ax</em>, long process or axis cylinder terminating in the tail end of the spinal cord; <em>n</em>, nucleus.

Nerve Cell

Nerve cell from the brain; a, processes by which it communicates with other cells near by;…

Front view of head of bee. <em>a</em>antenna; <em>e</em>, compound eye; the three black dots are the simple eyes.

Bee Head

Front view of head of bee. aantenna; e, compound eye; the three black dots are the…

A heavy border which shuts out a bleak field. In front of this border is an ideal place for flowers.

Border

A heavy border which shuts out a bleak field. In front of this border is an ideal place for flowers.

View of the Antarctic continent

Antarctica

View of the Antarctic continent