See also T.J. Kirkland and R.M. Kennedy,Historic Camden(Columbia, S.C., 1905).
See also T.J. Kirkland and R.M. Kennedy,Historic Camden(Columbia, S.C., 1905).
CAMEL(from the ArabicDjemalor the Heb.Gamal), the name of the single-humped ArabianCamelus dromedarius, but also applied to the two-humped central AsianC. bactrianusand to the extinct relatives of both. The characteristics of camels and their systematic position are discussed under the headingsTylopodaandArtiodactyla. The two living species are distinguishable at a glance. It may be mentioned that the Bactrian camel, which is a shorter-legged and more ponderous animal than the Arabian species, grows an enormously long and thick winter coat, which is shed in blanket-like masses in spring. The Arabian camel, which is used not only in the country from which it takes its name, but also in North Africa and India, and has been introduced into Australia and North America, is known only as a domesticated animal. On the other hand, the Bactrian species, which is employed throughout a large tract of central Asia in the domesticated condition, appears, according to recent researches, to exist in the wild state in some of the central Asian deserts. From the examination of specimens collected by Dr Sven Hedin, Professor W. Leche shows that the wild Bactrian camel differs from the domesticated breed of central Asia in the following external characters: the humps are smaller; the long hair does not occupy nearly so much of the body; the colour is much more rufous; and the ears and muzzle are shorter. Many important differences are also recorded between the skulls of the two animals, and it is especially noteworthy that the last lower molar is smaller in the wild than in the tame race. In connexion with this point it should be noticed that, unlike what occurs in the yak, the wild animal is not larger than the tame one, although it is incorrect to say that the former is decidedly the inferior of the latter in point of stature. Dr Leche also institutes a comparison between the skeletons of the wild and the tame Bactrian camel with the remains of certain fossil Asiatic camels, namely,Camelus knoblochifrom Sarepta, Russia, andC. alutensisfrom the Aluta valley, Rumania. This comparison leads to the important conclusion that the wild BactrianCamelus bactrianus feruscomes much nearer to the fossil species than it does to the domesticated breed, the resemblance being specially noticeable in the absolutely and relatively small size of the last molar. In view of these differences from the domesticated breed, and the resemblance of the skull or lower jaw to that of the extinct European species, it becomes practically impossible to regard the wild camels as the offspring of animals that have escaped from captivity.
On the latter hypothesis it has been generally assumed that the wild camels are the descendants of droves of the domesticated breed which escaped when certain central Asian cities were overwhelmed by sand-storms. This theory, according to Professor Leche, is rendered improbable by Dr Sven Hedin’s observations on the habits and mode of life of the wild camel. The habitat of the latter extends from the lower course of the Keria river to the desert at the termination of that river, and thence to the neighbourhood of the Achik, the ancient bed of the Tarim river. These animals also occur in the desert district south of the Tarim; but are most abundant in the deserts and mountains to the southward of Kuruktagh, where there are a few brackish-water pools, and are also common in the barren mountains between Kuruktagh and Choetagh. Large herds have also been observed in the deserts near Altyntagh. The capacity of camels for travelling long distances without water—owing to special structural modifications in the stomach—is familiar to all. That the Arabian species was one of the earliest animals to be domesticated is evident from the record of Scripture, where six thousand camels are said to have formed part of the wealth of the patriarch Job. Camels also formed part of the present which Pharaoh gave to Abraham, and it was to a company of Ishmaelites travelling from Gilead to Egypt on camels, laden with spices, much as their Arabian descendants do at the present day, that Joseph was sold by his brothers.
The hump (or humps) varies in size according to the condition of the animal, becoming small and flaccid after hard work and poor diet.
During the rutting-season male camels become exceedinglysavage and dangerous, uttering a loud bubbling roar and engaging in fierce contests with their fellows. The female carries her young for fully eleven months, and produces only one calf at a time, which she suckles for a year. Eight days after birth the young Arabian camel stands 3 ft. high, but does not reach its full growth till its sixteenth or seventeenth year; it lives from forty to fifty years. The flesh of the young camel resembles veal, and is a favourite food of the Arabs, while camel’s milk forms an excellent and highly nutritious beverage, although it does not furnish butter. The long hair is shorn every summer, and woven into a variety of stuffs used by the Arab for clothing himself and his family, and covering his tent. It was in raiment of camel’s hair that John the Baptist appeared as a preacher. The hair imported into Europe is chiefly used in the manufacture of small brushes used by painters, while the thick hide is formed into a very durable leather. The droppings are used as fuel, and from the incinerated remains of these sal-ammoniac is extracted, which was at one time largely exported from Egypt.
The Bactrian camel is, if possible, of still more importance to many of the central Asian Mongol races, supplying them alike with food and raiment. It is, however, as “the ship of the desert,” without which vast tracts of the earth’s surface could scarcely be explored, that the camel is specially valuable. In its fourth year its training as a beast of burden begins, when it is taught to kneel and to rise at a given signal, and is gradually accustomed to bear increasing loads. These vary in weight from 500 to 1000 lb., according to the variety of camel employed, for of the Arabian camel there are almost as many breeds as there are of the horse. When crossing a desert camels are expected to carry their loads 25 m. a day for three days without drink, getting a supply of water, however, on the fourth; but the fleeter breeds will carry their rider and a bag of water 50 m. a day for five days without drinking. When too heavily laden the camel refuses to rise, but on the march it is exceedingly patient under its burden, only yielding beneath it to die. Relieved from its load it does not, like other animals, seek the shade, even when that is to be found, but prefers to kneel beside its burden in the broad glare of the sun, seeming to luxuriate in the burning sand. When overtaken by a dust-storm it falls on its knees, and stretching its neck along the sand, closes its nostrils and remains thus motionless till the atmosphere clears; and in this position it affords some shelter to its driver, who, wrapping his face in his mantle, crouches behind his beast.
The food of the camel consists chiefly of the leaves of trees, shrubs and dry hard vegetables, which it is enabled to tear down and masticate by means of its powerful front teeth. As regards temperament, if, writes Sir F. Palgrave, “docile means stupid, well and good; in such a case the camel is the very model of docility. But if the epithet is intended to designate an animal that takes an interest in its rider so far as a beast can, that in some way understands his intentions, or shares them in a subordinate fashion, that obeys from a sort of submissive or half-fellow-feeling with his master, like the horse or elephant, then I say that the camel is by no means docile—very much the contrary. He takes no heed of his rider, pays no attention whether he be on his back or not, walks straight on when once set agoing, merely because he is too stupid to turn aside, and then should some tempting thorn or green branch allure him out of the path, continues to walk on in the new direction simply because he is too dull to turn back into the right road. In a word, he is from first to last an undomesticated and savage animal rendered serviceable by stupidity alone, without much skill on his master’s part, or any co-operation on his own, save that of an extreme passiveness. Neither attachment nor even habit impresses him; never tame, though not wide-awake enough to be exactly wild.”
For extinct camels seeTylopoda.
(R. L.*)
The Biblical expression (Matt. xix. 24, &c.), “it is easier for a camel to go through a needle’s eye,” &c., is sometimes explained by saying that the “needle’s eye” means the small gate which is opened in the great gate of a city, when the latter is closed for the night; but recent criticism (e.g.Post inHastings’ Dict., under “Camel”) throws doubt on this explanation, and assumes that the more violent hyperbole is intended. There is a various readingκάμιλος(cable) forκάμηλος(camel), but Cheyne, in theEncy. Biblica, rejects this (seeCable).
The Biblical expression (Matt. xix. 24, &c.), “it is easier for a camel to go through a needle’s eye,” &c., is sometimes explained by saying that the “needle’s eye” means the small gate which is opened in the great gate of a city, when the latter is closed for the night; but recent criticism (e.g.Post inHastings’ Dict., under “Camel”) throws doubt on this explanation, and assumes that the more violent hyperbole is intended. There is a various readingκάμιλος(cable) forκάμηλος(camel), but Cheyne, in theEncy. Biblica, rejects this (seeCable).
CAMELFORD, THOMAS PITT,1st Baron(1737-1793), English politician and art patron, was a nephew of the 1st earl of Chatham. He sat in parliament from 1761 till 1784, siding against his uncle and following George Grenville, who was also a relative; and in 1784 he was raised to the peerage. He dabbled in architecture and the arts generally, and was a prominent figure in the artistic circles of his day. His sonThomas Pitt, 2nd Baron Camelford (1775-1804), who succeeded him in 1793, had an adventurous and misspent career in the navy, but is principally remembered for his death in a duel with Mr Best on the 10th of March 1804, the title becoming extinct.
CAMELLIA,a genus or subgenus of evergreen trees or shrubs belonging to the natural order Ternstroemiaceae, with thick dark shining leaves and handsome white or rose-coloured flowers. The nameCamelliawas given by Linnaeus in honour of George Joseph Camellus or Kamel, a Moravian Jesuit who travelled in Asia and wrote an account of the plants of the Philippine Island, Luzon, which is included in the third volume of John Ray’sHistoria Plantarum(1704). Modern botanists are agreed that the tea-plant, placed by Linnaeus in a separate genus,Thea, is too nearly allied toCamelliato admit of the two being regarded as distinct genera.TheaandCamelliaare therefore now considered to represent one genus, which has been generally calledCamellia, but more correctlyThea, as this name was the earlier of the two. Under the latter viewCamelliais regarded as a subgenus or section ofThea. It contains about eight species, natives of India, China and Japan. Most of the numerous cultivated forms are horticultural products ofC. japonica, a native of China and Japan, which was introduced into Europe by Lord Petre in 1739. The wild plant has red flowers, recalling those of the wild rose, but most of the cultivated forms are double. In the varietyanemonaefloranearly all the stamens have become transformed into small petaloid structures which give the flower the appearance of a double anemone.
Another species,C. reticulata, a native of Hongkong, is also prized for its handsome flowers, larger than those ofC. japonica, which are of a bright rose colour and as known in cultivation semi-double or double.
BothC. sasanquaandC. drupifera, the former inhabiting Japan and China, the latter Cochin-China and the mountains of India, are oil-yielding plants. The oil ofC. sasanqua(of which sasankwa is the native Japanese name) has an agreeable odour and is used for many domestic purposes. It is obtained from the seeds by subjecting them to pressure sufficient to reduce them to a coarse powder, and then boiling and again pressing the crushed material. The leaves are also used in the form of a decoction by the Japanese women for washing their hair; and in a dried state they are mixed with tea on account of their pleasant flavour. The oil ofC. drupifera, which is closely allied toC. sasanqua, is used medicinally in Cochin-China. The flowers of these two species, unlike those ofC. japonicaandC. reticulata, are odoriferous.
Camellias, though generally grown in the cool greenhouse, are hardy in the south of England and the south-west of Scotland and Ireland. They grow best in a rich compost of sandy peat and loam, and should not be allowed to get too dry at the roots; a liberal supply of water is especially necessary during the flowering period. The best position—when grown out of doors—is one facing north or north-west, with a wall or hedge behind for protection from cold winds. July is the best time for planting; care must be taken that the roots are evenly spread, not matted into a ball.
The plants are propagated by layers or cuttings, and the single-flowered ones also by seeds. Cuttings are taken in August and placed in sandy peat or loam in a cold shaded frame. In the following spring those which have struck are placed in a gentle heat, and in September or October the rooted plants are potted off. Camellias are also propagated by grafting or inarching in early spring on stocks of the common variety ofC. japonica.
The scale insect sometimes attacks the camellia. To removethe white scale, the plants are washed with a sponge and solution of soft soap as soon as their growth is completed, and again before the buds begin to swell. The brown scale may be got rid of by repeated washings with one of the many insecticides, but it should be applied at a temperature of 90°.
CAMEO,a term of doubtful origin, applied in the first instance to engraved work executed in relief on hard or precious stones. It is also applied to imitations of such stones in glass, called “pastes,” or on the shells of molluscous animals. A cameo is therefore the converse of an intaglio, which consists of an incised or sunk engraving in the same class of materials. For the history of this branch of art, and for an account of some of its most remarkable examples, seeGem.
The origin of the word is doubtful and has been a matter of copious controversy. TheNew English Dictionaryquotes its use in a Sarum inventory of 1222,”lapis unus cameu”and”magnus camehu.”The word is in current use in the 13th century. Thus Matthew Paris, in his Life of Abbot Leofric of St Albans, in theAbbatum S. Albani Vitae,says:”retentis quibusdam nobilibus lapidibus insculptis, quos camaeos vulgariter appellamus.”In variant forms the word has found its way into most languages,e.g.Latin,camahutus, camahelus, camaynus; Italian,chammeo, chameo; French,camahieu, chemahou, camaut, camaieu. The following may be mentioned among the derivations that have been proposed:—von Hammer:camaut, the hump of a camel; Littré and others:camateum, an assumed Low Latin form fromκαματεύεινandκάματον; Chabouillet and Babelon:κειμήλια, treasures, connecting the word in particular with the dispersion of treasures from Constantinople, in 1204; King: Arabiccamea, an amulet.
For a bibliography of the question, see Babelon,Cat. des Camées ... de la Bibliothèque Nationale, p. iv.
CAMERA(a Latin adaptation of Gr.καμάρα, an arched chamber), in law, a word applied at one time to the English judges’ chambers in Serjeants’ Inn, as distinct from their bench in Westminster Hall. It was afterwards applied to the judges’ private room behind the court, and, hence, in the phrasein camera, to cases heard in private,i.e.in chambers. So far as criminal cases are concerned, the courts have no power to hear them in private, nor have they any power to order adults (men or women) out of court during the hearing. In civil proceedings at common law, it may also be laid down that the public cannot be excluded from the court; inMalanv.Young, 1889, 6 T.L.R. 68, Mr Justice Denman held that he had power to hear the casein camera, but he afterwards stated that there was considerable doubt among the judges as to the power to hear casesin camera, even by consent, and the case was, by consent of the parties, finally proceeded with before the judgeas arbitrator. In the court of chancery it is the practice to hear in private cases affecting wards of the court and lunatics, family disputes (by consent), and cases where a public trial would defeat the object of the action (Andrewv.Raeburn, 1874, L.R. 9 Ch. 522). In an action for infringement of a patent for a chemical process the defendant was allowed to state a secret processin camera (Badische Anilin und Soda Fabrikv.Gillman, 1883, 24 Ch. D. 156). The Court of Appeal has decided that it has power to sit in private; inMellorv.Thompson, 1885, 31 Ch. D. 55, it was stated that a public hearing would defeat the object of the action, and render the respondent’s success in the appeal useless. In matrimonial causes, the divorce court, following the practice of the ecclesiastical courts under the provisions of the Matrimonial Causes Act 1857, s. 22, hears suits for nullity of marriage on physical groundsin camera, but not petitions for dissolution of marriage, which must be heard in open court. It was also decided inDrucev.Druce, 1903, 19 T.L.R. 387, that, in cases for judicial separation the court has jurisdiction to hear the casein camera, where it is satisfied that justice cannot be done by hearing the case in public.
CAMERA LUCIDA,an optical instrument invented by Dr William Hyde Wollaston for drawing in perspective. Closing one eye and looking vertically downwards with the other through a slip of plain glass,e.g.a microscope cover-glass, held close to the eye and inclined at an angle of 45° to the horizon, one can see the images of objects in front, formed by reflection from the surface of the glass, and at the same time one can also see through the transparent glass. The virtual images of the objects appear projected on the surface of a sheet of paper placed beneath the slip of glass, and their outline can be accurately traced with a pencil. This is the simplest form of the camera lucida. The image (see fig. 1) is, however, inverted and perverted, and it is not very bright owing to the poor reflecting power of unsilvered glass. The brightness of the image is sometimes increased by silvering the glass; and on removing a small portion of the silver the observer can see the image with part of the pupil while he sees the paper through the unsilvered aperture with the remaining part. This form of the instrument is often used in conjunction with the microscope, the mirror being attached to the eye-piece and the tube of the microscope being placed horizontally.
About the beginning of the 19th century Dr Wollaston invented a simple form of the camera lucida which gives bright and erect images. A four-sided prism of glass is constructed having one angle of 90°, the opposite angle of 135°, and the two remaining angles each of 67½°. This is represented in cross-section and in position in fig. 2. When the pupil of the eye is held half over the edge of the prism a, one sees the image of the object with one half of the pupil and the paper with the other half. The image is formed by successive total reflection at the surfaces b c and a b. In the first place an inverted image (first image) is formed in the face b c, and then an image of this image is formed in a b, and it is the outline of this second image seen projected on the paper that is traced by the pencil. It is desirable for two reasons that the image should lie in the plane of the paper, and this can be secured by placing a suitable lens between the object and the prism. If the image does not lie in the plane of the paper, it is impossible to see it and the pencil-point clearly at the same time. Moreover, any slight movement of the head will cause the image to appear to move relatively to the paper, and will render it difficult to obtain an accurate drawing.
Before the application of photography, the camera lucida was of considerable importance to draughtsmen. The advantages claimed for it were its cheapness, smallness and portability; that there was no appreciable distortion, and that its field was much larger than that of the camera obscura. It was used largely for copying, for reducing or for enlarging existing drawings. It will readily be understood, for example, that a copy will be half-size if the distance of the object from the instrument is double the distance of the instrument from the copy.
(C. J. J.)
CAMERA OBSCURA,an optical apparatus consisting of a darkened chamber (for which its name is the Latin rendering) at the top of which is placed a box or lantern containing a convex lens and sloping mirror, or a prism combining the lens and mirror. If we hold a common reading lens (a magnifying lens) in front of a lamp or some other bright object and at some distance from it, and if we hold a sheet of paper vertically at a suitable distance behind the lens, we see depicted on the paper an image of the lamp. This image is inverted and perverted. If now we place a plane mirror (e.g.a lady’s hand glass) behind the lens and inclined at an angle of 45° to the horizon so as to reflect the rays of light vertically downwards, we can produce on a horizontal sheet of paper an unperverted image of the bright object (fig. 1),i.e.the image has the same appearance as the object and is not perverted as when the reflection of a printed page is viewed in a mirror. This is the principle of thecamera obscura, which was extensively used in sketching from nature before the introduction of photography, although it is now scarcely to be seen except as an interesting side-show at places of popular resort. The image formed on the paper may be traced out by a pencil, and it will be noticed that in this case the image is real—not virtual as in the case of the camera lucida. Generally the mirror and lens are combined into a single piece of worked glass represented in section in fig. 2. Rays from external objects are first refracted at the convex surfacea b,then totally reflected at the plane surfacea c,and finally refracted at the concave surfaceb c(fig. 2) so as to form an image on the sheet of paperd e.The curved surfaces take the place of the lens in fig. 1, and the plane surface performs the function of the mirror. The prisma b cis fixed at the top of a small tent furnished with opaque curtains so as to prevent the diffused daylight from overpowering the image on the paper, and in the darkened tent the images of external objects are seen very distinctly.
Quite recently, the camera obscura has come into use with submarine vessels, theperiscopebeing simply a camera obscura under a new name.
(C. J. J.)
History.—The invention of this instrument has generally been ascribed, as in the ninth edition of this work, to the famous Neapolitan savant of the 16th century, Giovanni Battista della Porta, but as a matter of fact the principle of the simple camera obscura, or darkened chamber with a small aperture in a window or shutter, was well known and in practical use for observing eclipses long before his time. He was anticipated in the improvements he claimed to have made in it, and all he seems really to have done was to popularize it. The increasing importance of the camera obscura as a photographic instrument makes it desirable to bring together what is known of its early history, which is far more extensive than is usually recognized. In southern climes, where during the summer heat it is usual to close the rooms from the glare of the sunshine outside, we may often see depicted on the walls vivid inverted images of outside objects formed by the light reflected from them passing through chinks or small apertures in doors or window-shutters. From the opening passage of Euclid’sOptics(c.300b.c.), which formed the foundation for some of the earlier middle age treatises on geometrical perspective, it would appear that the above phenomena of the simple darkened room were used by him to demonstrate the rectilinear propagation of light by the passage of sunbeams or the projection of the images of objects through small openings in windows, &c. In the book known as Aristotle’sProblems(sect. xv. cap. 5) we find the correlated problem of the image of the sun passing through a quadrilateral aperture always appearing round, and he further notes the lunated image of the eclipsed sun projected in the same way through the interstices of foliage or lattice-work.
There are, however, very few allusions to these phenomena in the later classical Greek and Roman writers, and we find the first scientific investigation of them in the great optical treatise of the Arabian philosopher Alhazen (q.v.), who died at Cairo ina.d.1038. He seems to have been well acquainted with the projection of images of objects through small apertures, and to have been the first to show that the arrival of the image of an object at the concave surface of the common nerve—or the retina—corresponds with the passage of light from an object through an aperture in a darkened place, from which it falls upon a surface facing the aperture. He also had some knowledge of the properties of concave and convex lenses and mirrors in forming images. Some two hundred years later, betweena.d.1266 and 1279, these problems were taken up by three almost contemporaneous writers on optics, two of whom, Roger Bacon and John Peckham, were Englishmen, and Vitello or Witelo, a Pole.
That Roger Bacon was acquainted with the principle of the camera obscura is shown by his attempt at solving Aristotle’s problem stated above, in the treatiseDe Speculis,and also from his references to Alhazen’s experiments of the same kind, but although Dr John Freind, in hisHistory of Physick,has given him the credit of the invention on the strength of a passage in thePerspectiva, there is nothing to show that he constructed any instrument of the kind. His arrangement of concave and plane mirrors, by which the realistic images of objects inside the house or in the street could be rendered visible though intangible, there alluded to, may apply to a camera on Cardan’s principle or to a method of aerial projection by means of concave mirrors, which Bacon was quite familiar with, and indeed was known long before his time. On the strength of similar arrangements of lenses and mirrors the invention of the camera obscura has also been claimed for Leonard Digges, the author ofPantometria(1571), who is said to have constructed a telescope from information given in a book of Bacon’s experiments.
Archbishop Peckham, or Pisanus, in hisPerspectiva Communis(1279), and Vitello, in hisOptics(1270), also attempted the solution of Aristotle’s problem, but unsuccessfully. Vitello’s work is to a very great extent based upon Alhazen and some of the earlier writers, and was first published in 1535. A later edition was published, together with a translation of Alhazen, by F. Risner in 1572.
The first practical step towards the development of the camera obscura seems to have been made by the famous painter and architect, Leon Battista Alberti, in 1437, contemporaneously with the invention of printing. It is not clear, however, whether his invention was a camera obscura or a show box, but in a fragment of an anonymous biography of him, published in Muratori’sRerum Italicarum Scriptores(xxv. 296), quoted by Vasari, it is stated that he produced wonderfully painted pictures, which were exhibited by him in some sort of small closed box through a very small aperture, with great verisimilitude. These demonstrations were of two kinds, one nocturnal, showing the moon and bright stars, the other diurnal, for day scenes. This description seems to refer to an arrangement of a transparent painting illuminated either from the back or the front and the image projected through a hole on to a white screen in a darkened room, as described by Porta (Mag. Nat.xvii. cap. 7) and figured by A. Kircher (Ars Magna Lucis et Umbrae), who notes elsewhere that Porta had taken some arrangement of projecting images from an Albertus, whom he distinguished from Albertus Magnus, and who was probably L.B. Alberti, to whom Porta also refers, but not in this connexion.
G.B.I.T. Libri-Carucci dalla Sommaja (1803-1869), in his account of the invention of the camera obscura in Italy (Histoire des sciences mathématiques en Italic,iv. 303), makes no mention of Alberti, but draws attention to an unpublished MS. of Leonardo da Vinci, which was first noticed by Venturi in 1797, and has since been published in facsimile in vol. ii. of J.G.F. Ravaisson-Mollien’s reproductions of the MSS. in the Institut de France at Paris (MS.D, fol. 8recto). After discussing the structure of the eye he gives an experiment in which the appearance of the reversed images of outside objects on a piece of paper held in front of a small hole in a darkened room, with their forms and colours, is quite clearly described and explained with a diagram, as an illustration of the phenomena of vision. Another similar passage is quoted by Richter from folio 404b of the reproduction of theCodice Atlantico,in Milan, published by the Italian government. These are probably the earliest distinct accounts of the natural phenomena of the camera obscura, but remained unpublished for some three centuries. Leonardo also discussed the old Aristotelian problem of the rotundity of the sun’s image after passing through an angular aperture, but not so successfully as Maurolycus. He has also given methods of measuring the sun’s distance by means of images thrown on screens through small apertures. He was well acquainted with the use of magnifying glasses and suggested a kind of telescope for viewing the moon, but does not seem to have thought of applying a lens to the camera.
The first published account of the simple camera obscura was discovered by Libri in a translation of theArchitectureofVitruvius, with commentary by Cesare Caesariano, one of the architects of Milan cathedral, published at Conio in 1521, shortly after the death of Leonardo, and some twenty years before Porta was born. He describes an experiment made by a Benedictine monk and architect, Dom Papnutio or Panuce, of the same kind as Leonardo’s but without the demonstration.
About the same time Francesco Maurolico, or Maurolycus, the eminent mathematician of Messina, in hisTheoremata de Lumine et Umbra, written in 1521, fully investigated the optical problems connected with vision and the passage of rays of light through small apertures with and without lenses, and made great advances in this direction over his predecessors. He was the first correctly to solve Aristotle’s problem, stated above, and to apply it practically to solar observations in a darkened room (Cosmographia, 1535). Erasmus Reinhold has described the method in his edition of G. Purbach’sTheoricae Novae Planetarum(1542), and probably got it from Maurolycus. He says it can also be applied to terrestrial objects, though he only used it for the sun. His pupil, Rainer Gemma-Frisius, used it for the observation of the solar eclipse of January 1544 at Louvain, and fully described the methods he adopted for making measurements and drawings of the eclipsed sun, in hisDe Radio Astronomico et Geometrico(1545). He says they can be used for observation of the moon and stars and also for longitudes. The same arrangement was used by Copernicus, Tycho Brahe, by M. Moestlin and his pupil Kepler—the latter applying it in 1607 to the observation of a transit of Mercury—also by Johann Fabricius, in 1611, for the first observations of sun-spots. It is interesting to note this early employment of the camera obscura in the field of astronomical research, in which its latest achievements have been of such pre-eminent value.
The addition of optical appliances to the simple dark chamber for the purpose of seeing what was going on outside, was first described by Girolamo Cardan in hisDe Subtilitate(1550), as noted by Libri. The sun shining, he fixed a round glass speculum (orbem e vitro) in a window-shutter, and then closing it the images of outside objects would be seen transmitted through the aperture on to the opposite wall, or better, a white paper screen suitably placed. The account is not very clear, but seems to imply the use of a concave mirror rather than a lens, which might be suggested by the wordorbem. He refers to Maurolycus’ work with concave specula.
We now come to Giovanni Battista della Porta, whose account of the camera obscura in the first edition of theMagia Naturalis,in four books (1558, lib. iv. cap. 2), is very similar to Caesariano’s—a darkened room, a pyramidal aperture towards the sun, and a whitened wall or white paper screens, but no lens. He discloses as a great secret the use of a concave speculum in front of the aperture, to collect the rays passing through it, when the images will be seen reversed, but by prolonging them beyond the centre they would be seen larger and unreversed. This is much the same as Cardan’s method published eight years earlier, but though more detailed is not very clear. He then notes the application to portraiture and to painting by laying colours on the projected images. Nothing is said about the use of a lens or of solar observations. The second edition, in which he in the same words discloses the use of a convex lens in the aperture as a secret he had intended to keep, was not published till 1589, thirty-one years after the first. In this interval the use of the lens was discovered and clearly described by Daniello Barbaro, a Venetian noble, patriarch of Aquileia, in his workLa Pratica della perspettiva(p. 192), published in 1568, or twenty-one years before Porta’s mention of it. The lens used by Barbaro was an ordinary convex or old man’s spectacle-glass; concave, he says, will not do. He shows how the paper must be moved till it is brought into the focus of the lens, the use of a diaphragm to make the image clearer, and also the application of the method for drawing in true perspective. That Barbaro was really the first to apply the lens to the camera obscura is supported by Marius Bettinus in hisApiaria(1645), and by Kaspar Schott in hisMagia Universalis(1657), the former taunting Porta with the appropriation.
In an Italian translation of Euclid’sOptica, with commentary, Egnacio Danti (1573), after discussing the effects of plane, convex and concave reflectors, fully describes the method of showing reversed images passing through an aperture in a darkened room, and shows how, by placing a mirror behind the aperture, unreversed images might be obtained, both effects being illustrated by diagrams. F. Risner, who died in 1580, also in hisOpticae(1606) very clearly explained the reversal of the images of the simple camera obscura. He notes the convenience of the method for solar observations and its previous use by some of the observers already mentioned, as well as its advantages for easily and accurately copying on an enlarged or reduced scale, especially for chorographical or topographical documents. This is probably the first notice of the application of the camera to cartography and the reproduction of drawings, which is one of its principal uses at the present time. In theDiversarum Speculationum Mathematicarum el Physicarum(1585), by the Venetian Giovanni Battista Benedetti, there is a letter in which he discusses the simple camera obscura and mentions the improvement some one had made in it by the use of a double convex lens in the aperture; he also says that the images could be made erect by reflection from any plane mirror.
Thus the use of the camera and of the lens with it was well known before Porta published his second edition of theMagia Naturalisin 1589. In this the description of the camera obscura is in lib. xvii. cap. 6. The use of the convex lens, which is given as a great secret, in place of the concave speculum of the first edition, is not so clearly described as by Barbaro; the addition of the concave speculum is proposed for making the images larger and clearer, and also for making them erect, but no details are given. He describes some entertaining peep-show arrangements, possibly similar to Alberti’s, and indicates how the dark chamber with a concave speculum can be used for observing eclipses. There is no mention whatever of a portable box or construction beyond the darkened room, nor is there in his later work,De Refractione Optices Parte(1593), in which he discusses the analogy between vision and the simple dark room with an aperture, but incorrectly. Though Porta’s merits were undoubtedly great, he did not invent or improve the camera obscura. His only novelty was the use of it as a peep-show; his descriptions of it are vague, but being published in a book of general reference, which became popular, he acquired credit for the invention.
The first to take up the camera obscura after Porta was Kepler, who used it in the old way for solar observations in 1600, and in hisAd Vitellionem Paralipomena(1604) discusses the early problems of the passages of light through small apertures, and the rationale of the simple dark chamber. He was the first to describe an instrument fitted with a sight and paper screen for observing the diameters of the sun and moon in a dark room. In his later book,Dioptrice(1611), he fully discusses refraction and the use of lenses, showing the action of the double convex lens in the camera obscura, with the principles which regulate its use and the reason of the reversal of the image. He also demonstrates how enlarged images can be produced and projected on paper by using a concave lens at a suitable distance behind the convex, as in modern telephotographic lenses. He was the first to use the termcamera obscura, and in a letter from Sir H. Wotton written to Lord Bacon in 1620 we learn that Kepler had made himself a portable dark tent fitted with a telescope lens and used for sketching landscapes. Further, he extended the work of Maurolycus, and demonstrated the exact analogy between the eye and the camera and the arrangement by which an inverted image is produced on the retina.
In 1609 the telescope came into use, and the danger of observing the sun with it was soon discovered. In 1611 Johann Fabricius published his observations of sun-spots and describes how he and his father fell back upon the old method of projecting the sun’s image in a darkened room, finding that they could observe the spots just as well as with the telescope. They do not seem to have used a lens, or thought of using the telescope for projecting an enlarged imase on Kepler’s principle. Thiswas done in 1612 by Christoph Schemer, who fully described his method of solar observation in theRosa Ursina(1630), demonstrating very clearly and practically the advantages and disadvantages of using the camera, without a lens, with a single convex lens, and with a telescopic combination of convex object-glass and concave enlarging lens, the last arrangement being mounted with an adjustable screen or tablet on an equatorial stand. Most of the earlier astronomical work was done in a darkened room, but here we first find the dark chamber constructed of wooden rods covered with cloth or paper, and used separately to screen the observing-tablet.
Various writers on optics in the 17th century discussed the principle of the simple dark chamber alone and with single or compound lenses, among them Jean Tarde (Les Astres de Borbon, 1623); Descartes, the pupil of Kepler (Dioptrique, 1637); Bettinus (Apiaria, 1645); A. Kircher (Ars Magna Lucis et Umbrae, 1646); J. Hevelius (Selenographia, 1647); Schott (Magia Universalis Naturae et Artis, 1674); C.F.M. Deschales (Cursus, seu Mundus Mathematicus, 1674); Z. Traber (Nervus Opticus, 1675), but their accounts are generally more interesting theoretically than as recording progress in the practical use and development of the instrument.
The earliest mention of the camera obscura in England is probably in Francis Bacon’sDe Augmentis Scientiarum, but it is only as an illustration of the projected images showing better on a white screen than on a black one. Sir H. Wotton’s letter of 1620, already noted, was not published till 1651 (Reliquiae Wottonianae, p. 141), but in 1658 a description of Kepler’s portable tent camera for sketching, taken from it, was published in a work calledGraphice, or the most excellent Art of Painting, but no mention is made of Kepler. In W. Oughtred’s English edition (1633) of theRécréations mathématiques(1627) of Jean Leurechon (“Henry van Etten”) there is a quaint description, with figures, of the simple dark chamber with aperture, and also of a sort of tent with a lens in it and the projection on an inner wall of the face of a man standing outside. The English translation of Porta’sNatural Magickwas published in 1658.
Robert Boyle seems to have been the first to construct a box camera with lens for viewing landscapes. It is mentioned in his essayOn the Systematic or Cosmical Qualities of Things(ch. vi.), written about 1570, as having been made several years before and since imitated and improved. It could be extended or shortened like a telescope. At one end of it paper was stretched, and at the other a convex lens was fitted in a hole, the image being viewed through an aperture at the top of the box. Robert Hooke, who was some time Boyle’s assistant, described (Phil. Trans., 1668, 3, p. 741) a camera lucida on the principle of the magic lantern, in which the images of illuminated and inverted objects were projected on any desired scale by means of a broad convex lens through an aperture into a room where they were viewed by the spectators. If the objects could not be inverted, another lens was used for erecting the images. From Hooke’sPosthumous Works(1705), p. 127, we find that in one of the Cutlerian lectures on Light delivered in 1680, he illustrated the phenomena of vision by a darkened room, or perspective box, of a peculiar pattern, the back part, with a concave white screen at the end of it, being cylindrical and capable of being moved in and out, while the fore part was conical, a double convex lens being fixed in a hole in front. The image was viewed through a large hole in the side. It was between 4 and 5 ft. long.
Johann Zahn, in hisOculus Artificialis Teledioptricus(1685-1686), described and figured two forms of portable box cameras with lenses. One was a wooden box with a projecting tube in which a combination of a concave with a convex lens was fitted, for throwing an enlarged image upon the focusing screen, which in its proportions and application is very similar to our modern telephotographic objectives. The image was first thrown upon an inclined mirror and then reflected upwards to a paper screen on the top of the box. In an earlier form the image is thrown upon a vertical thin paper screen and viewed through a hole in the back of the camera. There is a great deal of practical information on lenses in connexion with the camera and other optical instruments, and the book is valuable as a repertory of early practical optics, also for the numerous references to and extracts from previous writers. An improved edition was published in 1702.
Most of the writers already noticed worked out the problems connected with the projection of images in the camera obscura more by actual practice than by calculation, but William Molyneux, of Dublin, seems to have been the first to treat them mathematically in hisDioptrica Nova(1692), which was also the first work in English on the subject, and is otherwise an interesting book. He has fully discussed the optical theory of the dark chamber, with and without a lens, and its analogy to the eye, also several optical problems relating to lenses of various forms and their combinations for telescopic projection, rules for finding foci, &c. He does not, however, mention the camera obscura as an instrument in use, but in John Harris’sLexicon Technicum(1704) we find that the camera obscura with the arrangement called the “scioptric ball,” and known asscioptricks, was on sale in London, and after this must have been in common use as a sketching instrument or as a show.
Sir Isaac Newton, in hisOpticks(1704), explains the principle of the camera obscura with single convex lens and its analogy with vision in illustration of his seventh axiom, which aptly embodies the correct solution of Aristotle’s old problem. He also made great use of the simple dark chamber for his optical experiments with prisms, &c. Joseph Priestley (1772) mentions the application of the solar microscope, both to the small and portable and the large camera obscura. Many patterns of these two forms for sketching and for viewing surrounding scenes are described in W.J.’s Gravesande’sEssai de perspective(1711), Robert Smith’sCompleat System of Optics(1738), Joseph Harris’sTreatise on Optics(1775), Charles Hutton’sPhilosophical and Mathematical Dictionary, and other books on optics and physics of that period. The camera obscura was first applied to photography (q.v.) probably about 1794, by Thomas Wedgwood. His experiments with Sir Humphrey Davy in endeavouring to fix the images of natural objects as seen in the camera were published in 1802 (Journ. Roy. Inst.).