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"A genus of plants of the natural order Hydrocharideae, of which a species A. Canadensis has recently become naturalised in Britain, suddenly appearing in so great abundance as to impede the navigation of some rivers and canals." — Chambers' Encyclopedia, 1875

Anacharis

"A genus of plants of the natural order Hydrocharideae, of which a species A. Canadensis has recently…

"Star of the order of the Thistle." — Chambers' Encyclopedia, 1875

Order of the Thistle

"Star of the order of the Thistle." — Chambers' Encyclopedia, 1875

"A genus of Andromeda polifolia of plants of the natural order Ericaceae, distinguished by a 5-valve naked capsule, which splits up through the back of the cells; anthers with two awns, and a globose corolla with the orifice contracted." — Chambers' Encyclopedia, 1875

Andromeda

"A genus of Andromeda polifolia of plants of the natural order Ericaceae, distinguished by a 5-valve…

"A genus of plants of the natural order Ranunculaceae, having an involucre of three divided leaves, more or less remote from the flower, a petaloid calyx, searcely distinguishable from the corolla, and soft woolly achenia, which in some species have tails." — Chambers' Encyclopedia, 1875

Anemone Coronaria

"A genus of plants of the natural order Ranunculaceae, having an involucre of three divided leaves,…

"A genus of plants of the natural order Umbelliferae, by some botanists divided into two: A., and Archangelica. The species are mostly herbaceous and perennial, natives of the temperate and colder regions of the northern hemisphere. They have bipinnate or tripinnate leaves." — Chambers' Encyclopedia, 1875

Angelica

"A genus of plants of the natural order Umbelliferae, by some botanists divided into two: A., and Archangelica.…

"The religious Order of the Heavenly Annunciation, or of the Nuns of the Annunciation of Mary, was instituted by Victoria Fornare at Genoa in 1682, after the rule of St. Augustine. All the convents of the order in France, Germany, and the Netherlands have disappeared since the French Revolution. Some still exist in Italy." — Chambers' Encyclopedia, 1875

Order of the Annunciation

"The religious Order of the Heavenly Annunciation, or of the Nuns of the Annunciation of Mary, was instituted…

"A genus of plants of the natural order Leguminosae, sub-order Papilionaceae, natives of the warm parts of America, of which, until recently, the only known species was the A. hypogaea, sometimes called the underground kidney-bean, and more frequently the ground-nut. It also receives the names of earth-nut, American earth-nut, and mandubi." — Chambers' Encyclopedia, 1875

Arachis

"A genus of plants of the natural order Leguminosae, sub-order Papilionaceae, natives of the warm parts…

"A genus of plants of the natural order Coniferae, allied to the cypress, and consisting of evergreen trees and shrubs with compressed or flattened branchlets-small, scale-like, imbricated leaves-and monaecious flowers, which have 4-celled anthers, and the scales of the strobiles with two upright ovules." — Chambers' Encyclopedia, 1875

Arbor Vitae

"A genus of plants of the natural order Coniferae, allied to the cypress, and consisting of evergreen…

"A genus of plants of the natural order Aristolochiaceae. This order, which is dicotyledonous or exogenous, consists of herbaceous plants or shrubs, orten climbing shrubs, and contains upwards of 130 known species, chiefly natives of warm climates, and particularly abundant in the tropical regions of South America." — Chambers' Encyclopedia, 1875

Aristolochia

"A genus of plants of the natural order Aristolochiaceae. This order, which is dicotyledonous or exogenous,…

"A genus of plants of the natural order Aristolochiaceae. This order, which is dicotyledonous or exogenous, consists of herbaceous plants or shrubs, orten climbing shrubs, and contains upwards of 130 known species, chiefly natives of warm climates, and particularly abundant in the tropical regions of South America." — Chambers' Encyclopedia, 1875

Aristolochia

"A genus of plants of the natural order Aristolochiaceae. This order, which is dicotyledonous or exogenous,…

"A genus of plants belonging to the natural order compositae, sub-order Corymbiferae. The flowers of the ray are female and ligulate, those of the disk hermaphrodite and tubular. The receptacle is naked; the pappus hairy. The root, leaves, and flowers of the Mountain Tobacco are much valued in medicine, and administers in various forms as a stimulant in paralytic affections, typhoid fevers, and other diseases." — Chambers' Encyclopedia, 1875

Arnica Montana

"A genus of plants belonging to the natural order compositae, sub-order Corymbiferae. The flowers of…

"A plant of the natural order Umbelliefrae, a native of the elevated table-lands in the neighborhood of Santa Fe de Bogota and Caracas, and of regions of similar climate in other parts of Tropical America. It is much cultivated in its native country for its roots, which are used as an esculent. The root divides into a number of parts, which resemble cows' horns or large carrots. When boiled, they are firm and tender, with a flavor not so strong as that of a parsnip." — Chambers' Encyclopedia, 1875

Arracacha

"A plant of the natural order Umbelliefrae, a native of the elevated table-lands in the neighborhood…

"Artocarpaceae, a natural order of Dicotyledonous plants, of which the Bread-fruit is the type; very nearly allied to that of Moraceae, and, like it, by many botanists regarded as a sub-order of Urticaceae. The botanical distinction between Artocarpaceae and Moraceae lies chiefly in the straight embryo and large cotyledons of the former." — Chambers' Encyclopedia, 1875

Bread-fruit

"Artocarpaceae, a natural order of Dicotyledonous plants, of which the Bread-fruit is the type; very…

"A plant of the natural order Aristolochiaceae, a native of Europe, growing in woods; rare, and perhaps not truly indigenous, in Britain. The whole plant has acrid properties; the roots and leaves are aromatic, purgative, and emetic. b, detached anther; c, style." — Chambers' Encyclopedia, 1875

Asarabacca

"A plant of the natural order Aristolochiaceae, a native of Europe, growing in woods; rare, and perhaps…

"A genus of trees belonging to the natural order Oleaceae, and distinguished by very imperfect flowers, in which the calyx is obsolete, and the corolla either wanting or 3-4 partite; the fruit is a samara, a seed-vessel foliaceous at the extremity." — Chambers' Encyclopedia, 1875

Common Ash

"A genus of trees belonging to the natural order Oleaceae, and distinguished by very imperfect flowers,…

"A genus of plans of the natural order Leguminosae, sub-order Papilionaceae. The pod is more or less perfectly 2-celled. The leaves are pinnate, with a terminal leaflet. the species are numerous, natives chiefly of the temperate and colder parts of the Old World, shrubby, and often spiny, or unarmed and herbaceous." — Chambers' Encyclopedia, 1875

Astragalus

"A genus of plans of the natural order Leguminosae, sub-order Papilionaceae. The pod is more or less…

"By anatomists, the auditory nerve is associated with the facial, and is the seventh in order of origin from the brain, counting from before backwards. The seventh pair consists of the portio dura or facial, the portio mollis or auditory, and a small intermediate portion." — Chambers' Encyclopedia, 1875

Auditory Nerve

"By anatomists, the auditory nerve is associated with the facial, and is the seventh in order of origin…

"By anatomists, the auditory nerve is associated with the facial, and is the seventh in order of origin from the brain, counting from before backwards. The seventh pair consists of the portio dura or facial, the portio mollis or auditory, and a small intermediate portion." — Chambers' Encyclopedia, 1875

Auditory Nerve

"By anatomists, the auditory nerve is associated with the facial, and is the seventh in order of origin…

"An order of knighthood in Portugal, instituted by Sancho, the first king of Portugal, in imitation of the order of Calatrava, and having, like it, for its object the subjection of the Moors." — Chambers' Encyclopedia, 1875

Aviz

"An order of knighthood in Portugal, instituted by Sancho, the first king of Portugal, in imitation…

"The god of wine, was the son of Zeus and Semele, the daughter of Cadmus. Before his birth, Semele fell a victim to the insidious counsels of the jealous Here, who induced her to petition Zeus to visit her in his proper form and majesty." — Chambers' Encyclopedia, 1875

Bacchus

"The god of wine, was the son of Zeus and Semele, the daughter of Cadmus. Before his birth, Semele fell…

"An erect, branching perennial, herbaceous plant of the natural order Labiatae, a native of the south of Europe, naturalised in a few places in England." — Chambers' Encyclopedia, 1875

Balm

"An erect, branching perennial, herbaceous plant of the natural order Labiatae, a native of the south…

"A genus of plants of the natural order Labiatae. The species are all natives of the tropics, or of the warmer temperate parts of the world, and are generally characterized by a pleasant aromatic smell and taste." — Chambers' Encyclopedia, 1875

Basil

"A genus of plants of the natural order Labiatae. The species are all natives of the tropics, or of…

"A genus of exogenous plants, which gives its name to the natural order Cistaceae; an order allied to Cruciferae and Capparideae, and containing about 200 known species of shrubs and herbaceous plants, chiefly natives of the south of Europe and north of Africa." — Chambers' Encyclopedia, 1875

Rock-Rose

"A genus of exogenous plants, which gives its name to the natural order Cistaceae; an order allied to…

"A genus of plants of the natural order ranuculaceae having four colored sepals, no corolla, and fruit numerous one-seeded achaenia with long- generally feathery- awns. The species are pretty numerous, herbs or shrubs, generally with climbing stems, natives of very different climates, and much scattered over the world." — Chambers' Encyclopedia, 1875

Clematis

"A genus of plants of the natural order ranuculaceae having four colored sepals, no corolla, and fruit…

"Cloves are the flower-buds of the Clove-tree. The genus to which this tree belongs is of the natural order Myrtaceae; the calyx has a cylindrical tube and 4-cleft border; the corolla consists of four petals united by their tips; the stamens are in four clusters; and the fruit is an oblong dry berry with one or two cells and as many seeds." — Chambers' Encyclopedia, 1875

Cloves

"Cloves are the flower-buds of the Clove-tree. The genus to which this tree belongs is of the natural…

"A genus of plants of the natural order Melanthaceae. The species, which are few in number, are stemless, with flowers half subterranean like the crocus, the limb of the perianth and part of the tube only rising above ground. The floews much resemble crocus-flowers, but are readily distinguished by having six instead of three stamens, and three styles instead of one." — Chambers' Encyclopedia, 1875

Colchicum

"A genus of plants of the natural order Melanthaceae. The species, which are few in number, are stemless,…

"A medicine once in much repute against low fevers, and as a mild stimulant and diaphoretic, and still used in some countries, although not much in Britain, consists of the root-stocks (rhizomes) of different species of Dorstenia, a tropical American plant of the natural order Moraceae. The genus is remarkable for the plane receptacle in which the numerous small flowers are fixed; the male flowers in superficial depressions the female flowers in deep sockets." — Chambers' Encyclopedia, 1875

Contrayerva

"A medicine once in much repute against low fevers, and as a mild stimulant and diaphoretic, and still…

"A valuable medicinal substance, consisting chiefly of a resin (Resin of Copaiva) and a volatile oil (Oil of Copaiva). It flows from incisions made in the stems of trees of the genus Copaifera, trees with pinnate leaves, of the natural order Leguminosae, sub-order Caesalpinisae, natives of the topical parts of America." — Chambers' Encyclopedia, 1875

Copaiva Tree

"A valuable medicinal substance, consisting chiefly of a resin (Resin of Copaiva) and a volatile oil…

"A genus of plants of the natural order Umbelliferae, having petals bent in at the middle, and flat compressed fruit. One species only is a native of Britain, the common cow parsnip is hog-weed, called Kiesh in Scotland; a common and rank weed, with coarsely hairy leaves, and stem about 3-5 feet high." — Chambers' Encyclopedia, 1875

Cow Parsnip

"A genus of plants of the natural order Umbelliferae, having petals bent in at the middle, and flat…

"A name given to many plants, of which the foliage has a pungent, mustard-like taste, and is used as a salad. It is sometimes more strictly confused to the genus Lepidium, a genus of the natural order Cruciferae, having small white flowers, and oblong or rounded laterally compressed pouches (silicules), with the cells one-seeded, and the valves keeled or winged on the back." — Chambers' Encyclopedia, 1875

Cress

"A name given to many plants, of which the foliage has a pungent, mustard-like taste, and is used as…

"A small procumbent shrub, of the natural order Empetraceae, a native of the northern parts of the world, abundant in the moors of Scotland and the north of England. The order consists of a few heath-like shrubs, which, however, are regarded as having a botanical affinity to Euphorbiaceae, with small unisexual flowers in the axils of the leaves, the fruit a small berry seated in the persistent calyx. b, fruit cut open; c, flower." — Chambers' Encyclopedia, 1875

Crowberry

"A small procumbent shrub, of the natural order Empetraceae, a native of the northern parts of the world,…

"The name commonly given in the West Indies and other tropical countries to the fruits of certain species of Anona, a genus of trees of the natural order Anonaceae. Some of the fruits of this genus are among the most delicious produced in tropical countries, as the Charimoyer, and even the common custard apple, which is regarded as a native of America, but is now very superior even to the West Indian." — Chambers' Encyclopedia, 1875

Custard Apple

"The name commonly given in the West Indies and other tropical countries to the fruits of certain species…

"A genus of plants of the natural order Thymeleaceae, having a 4-cleft, funnel-shaped perianth, the throat of which is destitute of scales, eight stamens, and one-seeded succulent fruit." — Chambers' Encyclopedia, 1875

Daphne Mezereon

"A genus of plants of the natural order Thymeleaceae, having a 4-cleft, funnel-shaped perianth, the…

"A genus of plants of the natural order Liliaceae, having a perianth with bell-shaped limb, and sub-cylindrical tube, and globose seeds with soft testa. Several species are cultivated in our flower-gardens, especially the fragrant Yellow Day-lily, a native of Hungary, Siberia, and the north of China." — Chambers' Encyclopedia, 1875

Day-lily

"A genus of plants of the natural order Liliaceae, having a perianth with bell-shaped limb, and sub-cylindrical…

"A genus of plants of the natural order Fumariaceae, in appearance and habit much resembling fumitories of extraordinary size. Dielytra spectabilis, a native of Siberia and the northern provinces of China, was introduced into Britain from the island of Chusan in 1846, and rapidly became a general favorite, on account of its long racemes of drooping, delicate, rosy-pink flowers." — Chambers' Encyclopedia, 1875

Dielytra

"A genus of plants of the natural order Fumariaceae, in appearance and habit much resembling fumitories…

"A very curious and interesting genus of plants of the natural order Droseraceae, having a 5-partite calyx, 5 petals, 10-20 stamens, and one style, with 5 closely united stigmata. Only one species is known, Dionaea muscipula, sometimes called Venus's Fly-trap and the Carolina Catchfly Plant." — Chambers' Encyclopedia, 1875

Dionaea

"A very curious and interesting genus of plants of the natural order Droseraceae, having a 5-partite…

"A genus of plants of the natural order Rutaceae, having a short 5-partite calx, five some-what unequal petals, ten stamens, and five 1—3 seeded follicular capsules cohering at the base." — Chambers' Encyclopedia, 1875

Dittany

"A genus of plants of the natural order Rutaceae, having a short 5-partite calx, five some-what unequal…

"A tree of the natural order Liliaceae, remarkable for the size which it sometimes attains, rivalling even the baobab, and of which a celebrated specimen near Orotava, in the island of Tenerife, was found by Humboldt in 1799 to have a stem about 45 feet in circumference, and is described as having been of similar gigantic size in the beginning of the 15th century." — Chambers' Encyclopedia, 1875

Dragon Tree

"A tree of the natural order Liliaceae, remarkable for the size which it sometimes attains, rivalling…

"Star of the Order of the Black Eagle." — Chambers' Encyclopedia, 1875

Black Eagle

"Star of the Order of the Black Eagle." — Chambers' Encyclopedia, 1875

"A wood remarkable for its hardness, heaviness, and deep black color, is the heart-wood of different species of Diospyros, of the natural order Ebenaceae, the same genus which produces the Date Plum, Kaki, and other fruits." — Chambers' Encyclopedia, 1875

Ebony

"A wood remarkable for its hardness, heaviness, and deep black color, is the heart-wood of different…

"A, Cerianthus solitarius. B, Transverse section of the stomodaeum, showing the sulculus, sl, and the arrangement of the mesenteries. C, Oral aspect of Arachnactis brachiolata, the larva of Cerianthus, with seven tentacles. D, Transverse section of an older larva. The numerals indicate the order of development of the mesenteries." — The Encyclopedia Britannica, 1910

Cerianthus Solitarius

"A, Cerianthus solitarius. B, Transverse section of the stomodaeum, showing the sulculus, sl, and the…

"The various phases of germination of spores of Bacillus ramosus, as actually observed in hanging drops under very high powers. Similar series of phases in the order of the small letters in each case, and with the times of observation attached. At f and g occurs the breaking up of the filament into rodlets." — The Encyclopedia Britannica, 1910

Bacillus Ramosus

"The various phases of germination of spores of Bacillus ramosus, as actually observed in hanging drops…

"The various phases of germination of spores of Bacillus ramosus, as actually observed in hanging drops under very high powers. Similar series of phases in the order of the small letters in each case, and with the times of observation attached. At f and g occurs the breaking up of the filament into rodlets." — The Encyclopedia Britannica, 1910

Bacillus Ramosus

"The various phases of germination of spores of Bacillus ramosus, as actually observed in hanging drops…

"Various stages in the development of the endogenous spores in a Clostridium — the small letters indicate the order." — The Encyclopedia Britannica, 1910

Spores

"Various stages in the development of the endogenous spores in a Clostridium — the small letters…

"Raspberry (Rubus idaeus, order Rosaceae), being fertilized. A, Flower. p, p, Petals. a, a, Anthers. s, Stigma. no, Nectary openings. nc, Nectar Cells. D, Drupels." — The Encyclopedia Britannica, 1910

Raspberry Fertilization

"Raspberry (Rubus idaeus, order Rosaceae), being fertilized. A, Flower. p, p, Petals. a, a, Anthers.…

"A genus of annual, subshrubby plants, order Solanaceae, with a wheel-shaped corolla, projecting and converging stamens, and a many-seeded berry. They are chiefly natives of the East and West Indies, China, Brazil, and Egypt, but have spread to various other tropical or subtropical countries, being cultivated for their fruit, which in some reaches the size of an orange, is fleshy and variously colored and contains a pungent principle, which is presented also and more largely in the seed." — Winston's Encyclopedia, 1919

Capsicum

"A genus of annual, subshrubby plants, order Solanaceae, with a wheel-shaped corolla, projecting and…

"A genus of order Piperaceae. The Piper nigrum, which furnishes the black pepper of commerse, is a native of the East Indies, where it is cultivated on an extensive scale. It is a climbing plant, which broad, ovate, acuminate leaves, and little globular berries, which, when ripe, are of a bright-red color. The pepper of Malacca, Java, and especially of Sumatra, is the most esteemed. Its culture has been introduced into various other tropical countries. White pepper is the best and soundest of the berries, gathered when fully ripe, and deprived of their external skin." — Winston's Encyclopedia, 1919

Black Pepper

"A genus of order Piperaceae. The Piper nigrum, which furnishes the black pepper of commerse, is a native…

"The root used in medicine under this name is obtained from Cephaelis Ipecacuanha, A. Rich, a small shrubby plant of the natural order Cinchonaceae. It is a native of Brazil, growing in clumps or patches in moist shady forests from 8 degrees to 22 degrees S. lat., and is believed to extend to the Bolivian province of Chiquitos, and the calley of Catica in New Granada." — The Encyclopedia Britannica, 1893

Ipecacuanha Plant

"The root used in medicine under this name is obtained from Cephaelis Ipecacuanha, A. Rich, a small…

"Botanically Jasminum, a genus of shrubs or climbers constituting the principal part of the natural order Jasminaceae, and comprising about sixty species, of which forty or more occur in the gardens of Britain. The plants of the genus are mostly natives of the warmer regions of the Old World, but there are one or two South American species. The leaves are pinnate or ternate, articulted to the petiole. The flowers, usually white or yellow, are arranged in terminal or axillary panicles, and have a tubular 5 or 8-cleft calyx, and a cylindrical corolla-tube, with a spreading limb, two included stamens, and a two-celled ovary." — The Encyclopedia Britannica, 1893

Jasmine

"Botanically Jasminum, a genus of shrubs or climbers constituting the principal part of the natural…

"Why does a person carrying a weight upon his back stoop forward? In order to bring the center of gravity of his body and the load over his feet. If held in this position, he would fall backwards, as the direction of the center of gravity would fall beyond his heels." — Wells, 1857

Center of Gravity

"Why does a person carrying a weight upon his back stoop forward? In order to bring the center of gravity…

"Why does a person carrying a weight upon his back stoop forward? In order to bring the center of gravity of his body and the load over his feet, he assumes this position." — Wells, 1857

Center of Gravity

"Why does a person carrying a weight upon his back stoop forward? In order to bring the center of gravity…

A diagram showing the titles for different types of architecture.

Elements of an Architectural Order

A diagram showing the titles for different types of architecture.

"The external bones of the temple are supposed to be removed in order to render visible the muscular arrangements. The muscle, 1, raises the eye-lid, and is constantly in action while we are awake. During sleep, the muscle being in repose and relaxed, the eye-lid falls and protects the eye from the action of light. The muscle, 4, turns the eye upwards; 5, downwards; 6, outwards; and a corresponding one on the inside, not seen in the figure, turns it inwards. No. 2 and 10 turn the eye round its axis. No. 11 is the great optic nerve, which conveys the sensation to the brain. If this nerve were cut, notwithstanding the eye might be in other respects perfect, the sense of sight would be destroyed." —Wells, 1857

Eye Muscles

"The external bones of the temple are supposed to be removed in order to render visible the muscular…

"Next in order is the aqueous humor, b, e, in the middle of which is the iris, d, c. Behind the pupil we have the crystalline lens, f, and then the vitreous humor, h, filling all the interior of the ball of the eye. m indicates the retina, which is an expansion of the optic nerve, n. k is the choroid coat, a membrane interposed between the retina and the sclerotic coat; it terminates in form in a series of folds or filaments, g, called the ciliary ligament or process." —Wells, 1857

Eye

"Next in order is the aqueous humor, b, e, in the middle of which is the iris, d, c. Behind the pupil…

"In order to produce, on the catoptric system, a fixed light showing all round the circle, a number of reflectors are fixed round the outside of a stationary chandelier n. As the ordinary paraboloid has about 14 degrees of divergence, twenty-five reflectors were needed to light up continuously (though not equally) the whole horizon." —The Encyclopedia Britannica, 1910

Revolving Light

"In order to produce, on the catoptric system, a fixed light showing all round the circle, a number…

"In order strictly to equalize a fixed light over the whole horizon, which could not possibly be done with separate reflectors, Marcet proposed this ingenious instrument, which is generated by the revolution of the parabolic profile pp' round its parameter as a vertical axis, instead of round a horizontal axis, as in all former reflectors." —The Encyclopedia Britannica, 1910

Parabolic Profile

"In order strictly to equalize a fixed light over the whole horizon, which could not possibly be done…

"Fresnel next conceived the admirable improvement of employing the principle of "total" or internal reflexion by glass prisms. The ray Fi falling on a prismoidal ring, ABC, is refracted and bent in the direction iR, and falling on the side AC, at an angle of incidence greater than the critical, is totally relfected in the direction Re, and, impinging on the side BC at e, it undergoes a second refraction, and emerges horizontally. The highest ray FA after refraction by AB and reflexion by AC must (in order to avoid superfluous glass) pass along AB, and after a second refraction at B emerge horizontally. The lowest ray FB after refraction by AC and a second refraction by BC also emerge horizontally." —The Encyclopedia Britannica, 1910

Reflecting Prism

"Fresnel next conceived the admirable improvement of employing the principle of "total" or internal…

"The pump barrel, a, b, is represented as divided lengthwise, in order to show the inside. The piston, c, is fitted so accurately to the barrel, as to work up and down water tight; both barrel and piston being made of iron. The thing to be broken or pressed, is laid on the flat surface, i, there being above this, a strong frame to meet the pressure, not shown in the figure. The small forcing pump, of which d is the piston, and h, the lever by which it is worked, is also made of iron." —Comstock, 1850

Hydraulic Press

"The pump barrel, a, b, is represented as divided lengthwise, in order to show the inside. The piston,…

"Take a piece of ivory, or any other substance that will sink in water, and weigh it accurately in the usual manner; then suspend it by a thread, or hair, in the empty cup a, and balance it. Now pour water into the cup, and it will be found that the suspended body will lose a part of its weight, so that a certain number of grains must be taken from the opposite scale, in order to make the scales balance as before the water was poured in. The number of grains taken from the opposite scale, show the weight of a quantity of water equal to the bulk of the body so suspended." —Comstock, 1850

Water Weighing

"Take a piece of ivory, or any other substance that will sink in water, and weigh it accurately in the…

"Camera obscura strictly signifies a darkened chamber, because the room must be darkened, in order to observe its effects. To witness the phenomena of this instrument, let a room be closed in every direction, so as to exclude the light. Then from an aperture, say of an inch in diameter, admit a single beam of light, and the images of external things, such as trees and houses, and persons walking the streets, will be seen inverted on the wall opposite to where the light is admitted, or on a screen of white paper, placed before the aperture. The reason why the image is inverted will be obvious, when it is remembered that the rays proceeding from the extremities of the object must converge in order to pass through the small aperture; and as the rays of light always proceed in straight lines, they must cross each other at the point of admission. Thus the pencil a, coming from the upperpart of the tower, and proceeding straight, will represent the image of the part at b, while the lower part c, for the same reason, will be represented at d." —Comstock, 1850

Camera Obscura

"Camera obscura strictly signifies a darkened chamber, because the room must be darkened, in order to…