CAMERA OBSCUBA. 84 CAMEBABIUS. a small circular hole in the shutter, images of the objects outside will be thrown on any sur- face facing the hole, and will he reversed. Such was the condition of the camera until the time of Cardan, about the middle of the Sixteenth Centurj-, when he improved it by the addition of a convex lens at the aperture. The instru- ment in this form is descril)e<l in his work De Subtilitate. In ITilift Giambattista della Porta, of Naples, to whom the invention is generally as- cribed, in the seventh book of his work on Natural Magic, gives a detailed description of the apparatus, and in his instrument he placed an inclined mirror before the lens, with the re- sult that the pictures were rendered brighter and erect, instead of inverted. Porta's camera obscura attracted general attention, and the in- strument was soon provided for the coiuitry houses of the wealthy, being placed usually in a small conical building, with a white table or surface in the centre, on which the pictures were projected. A more modern form is shown in Fig- 1- The camera obscura in the form of a box, with inclined mirror and a piece of ground glass or paper on which the images could be traced, was invented by Hooke in 16V9. This instru- ment has since "become familiar in the form of an optical toy, shown in diagram in Fig. 2, FIG. i. I'AMEHA OBSCURA. though the same principle has been made use of in certain pieces of scientific apparatus. The camera obscura in its sinple form of lens and screen, suitably incased, was first used for pho- tographic work by Humphry Davy in 1802, at a time when he was engaged in exiierinients with Wedgwood. After this, the camera ob- scura WHS used by all the early experimenters in photography (q.v.). and the instrument has since been developed and amplified to a remark- able degree. Tlie photographic camera is con- PIG. 3. SIMPLE PHOTOGRAPHIC CAMERA. structed in an almost infinite variety of styles, depending in the main on the purpose for which it is to be used. In general, it c(msists of two boxes, joined by a flexible and light-proof ma- terial, such as "a Ixdlows of leather, rubber, or cloth, and susceptilile of l)t>ing moved toward or from each other, so that the distance be- tween the lens and focal plane or position where the image is received can be varied. In one of these boxes, or on an upright board taking its place, the lens is mounted, and on the other there is a frame carrying a piece of ground glass, which, at the time of taking the picture, is removed and the sensitive plate or film sub- stituted. This is contained in a holder so con- structed that the sensitive surface occupies the same position as the original focusing glass. • The construction of a camera varies with the use or process for which it is intended. Thus, for out-of-door work portability and rapidity of adjustment are essential, whereas in a studio or laboratory rigidity and adaptability are de- manded. A view camera does not require any considerable length of bed, or base, as the ground glass is never distant from the lens a much greater amount than the principal focus (q.v.), as the pictures are generally on a reduced scale. If a camera, however, is designed for copying or enlarging, then it must have a long bed, as the distance from the lens to the ground glass will be as many times greater than the distance be- tween the original object and the lens as it is de- sired to enlarge the picture. Frequently in the case of hand-cameras the ground glass is omitted, and the proper focus is obtained by reference to a graduated scale on the bed, on which are marked the foci corresponding to different distances. The use of films and increased ease of ma- nipulation has made photography universally popular, and there are almost as many styles of cameras as there are individual tastes. See arti- cle PHOTOCiRArilY. CAM'EBA'BITJS, Joachim (1500-74). A distinguislied (ierman classicist, born at Bam- berg, April 12, 1500, of a family which original- ly bore the name Liebhard ; for this Camerarius ((Jer. Kammermeister) was substituted, since the office of chamberlain to the Prince-Bisho]) of Bamberg was hereditary in the family. At the age of thirteen, Camerarius entered the Universi- ty of Leipzig, where the influence of (leorg Held, with wliom he was on intimate terms, led him to devote himself to the classics. He eventually was second only to Melanchthon (q.v.) in arousing an interest in classical study in Germany. In 1518 he began to teach tircck at Erfurt, but in 1521 he moved to Wittenberg, where he attached himself to Melanchthon. .4t the latter's recommendation, he was appointed to teach Creek and history in Nuremberg in 1520. Nine years later he was called to the University of Tiibingen as professor of the Creek and Latin literatures. In 1541 he went to Leip- zig, where he continued to lecture until his death, A|)ril 17. 1574. He ccmtributed to the eminence of this university, not only by his teaching and writing, but al.so by the practical measures of university reform which he, with certain asso- ciates, was able to carry through. He was espe- cially distinguished for his critical judgment, in which he surpassed Melanchthon, while his knowledge of the classics was not inferior to that of his friend, so that he deserves to be regarded as the greatest German classicist of his century. His works were very numerous. Besides biographical and tlicological writings, the most imjiortant are the following editions: Homeric Poems, with the so-called scholia of Pidymus (Basel, 1541); Oreek Eleqiac Poets (Basel, 1550); Theocritus
