n. In ancient architecture, an arched roof, ceiling, or covering; a vault.n. Nautical, a small vessel used on the coasts of the Bosporus and the Black Sea. Also camara.n. The variety of camera obscura used by photographers.n. In anatomy: The so-called fifth ventricle of the brain, between the laminæ of the septum lucidum.n. Some other chambered or vaulted part or organ, as the pericardium (camera cordis, chamber of the heart), the cranial cavity (camera cranii), etc.n. (Latin, clear chamber), an invention of the chemist Wollaston, designed to facilitate the delineation of distant objects. It consists of a solid prismatic piece of glass mounted upon a brass frame. The prism has its angles so arranged that the rays from the object appear reflected as shown below, and is covered at the top by a metallic eyepiece, the hole in which lies half over the edge of the prism, so as to afford a person looking through it a view of the picture reflected through the glass, and a direct view of his pencil or tracing-point. In the figure the object to be traced, f, is opposite the perpendicular surface of the prism, d c, and the rays proceeding from f pass through this surface and fall on the inclined plane c, b, which makes an angle with d c of 67½°; from this they are totally reflected to the plane b a, which makes an angle of 135° with b c, and are again reflected to the eye at e above the horizontal plane, which makes an angle of 67½° with the plane a b. The rays of light from the object proceeding upward from h toward the eye of the observer, he sees the image at m, and by placing the paper below in this place the image may be traced with a pencil. The brass frame of the prism has usually two lenses, one concave and the other convex, the former to be used in front between f and d c for nearsighted persons, and the latter at e for those who are farsighted. The size of the picture may also be increased or diminished by lengthening or shortening brass tubes connected with the frame. This instrument has undergone various modifications. It is extremely convenient on account of its portability.n. (Latin, dark chamber), an apparatus in which the images of external objects, received through a convex lens, are exhibited distinctly and in their natural colors on a white surface placed at the focus of the lens. The simplest form of this instrument consists of a darkened chamber, into which no light is permitted to enter except by a small hole in the window-shutter. An image of the objects opposite the hole will then appear on the wall, or on a white screen so placed as to receive the light coming from the opening. A convex lens may be fixed in the hole of the shutter. Portable cameras are constructed of various forms, but the design of them all is to throw the images of external objects, as persons, houses, trees, landscapes, etc., upon a plane or curved surface, for the purpose of drawing, the making of photographic pictures, or mere amusement. The surface on which the image is thrown may be covered with a sheet of paper, on which the figure may be traced by hand with a pencil; but the picture is most distinctly seen when the image is formed on the back of a silvered mirror. The figure represents a portable camera obscura. The camera obscura is often made in the form of a circular building capable of holding a number of people, who stand about a plain white table which is placed in the center of the structure, and on which the luminous image is projected by a lens on the roof. By turning the lens around, a panorama of the neighboring scenery is exhibited on the table. Cameras for use in sketching are made in the shape of a cone, with a lens and a reflecting mirror at the apex and a drawing-table inside. One side of the box is cut out, and at this opening the artist sits, partly enveloped by a dark curtain which serves to shut out extraneous light. See optigraph.n. A chamber, as of a house, a mine, a gun, etc.; any inclosure with a roof.n. A box-shaped device for viewing tubes containing colored solutions by transmitted light, the eyes being shielded from other light.n. In zoology, same as air-chamber, 4.
