Terminology

Leonardo, Vol. 13, p. 241. Pergamon Press, 1980. Printed in Great Britain. TERMINOLOGY The terms defined below were selected from artists' Articles and Notes published in the previous issue of Leonardo. Each definition is followed by an indication of the volume and page of Leonardo on which the term first appears. The terms were not found in the art dictionaries among the dictionaries listed in Leonardo 13, 63 (1980) or they are used in a new sense. Some are terms that have been carried over into the field of art from the natural and social sciences, from mathematics and from technology. Numbers in brackets, e.g. [11, 17], refer to the dictionaries mentioned above. The definitions are not presumed to be unassailable. The editors would, therefore, welcome the comments of readers on the definitions presented . 1011. Brownian motion (in physics)-The random motion of microscopic particles suspended in liquids or in gases resulting from the impact of molecules of the fluid surrounding the particles. The random motion is highly correlated, because the next location of a particle will be close to its previous location. [18] (d. Term 1012: Brownian or brown music and Term 1013: Brownian noise) 1012. Brownian or brown music-A term coined by Richard F. Voss to define music that exhibits the characteristics of Brownian motion and Brownian noise, for example a sequence of random tones is highly correlated by the constraint that each successive tone is close to the frequency and amplitude of the preceding tone. [M. Gardner, White and Brown Music, Fractal Curves and One-over-f Fluctuations, Scientific American, p. 16 (April 1978)] (cf. Term 1011: Brownian motion and Term 1013: Brownian noise) 1013. Brownian noise (in acoustics and information theory)-A kind of noise in which the spectral density or distribution of amplitude as function of frequency of sound is inversely proportional to the square of the frequency. Brownian motion also has this characteristic. (13, 137) (d. Term 1011: Brownian motion and Term 1012: Brownian or Brown music) 1014. Circle of fifths (in music)-The circular, clockwise arrangement of the 12 keys of a well-tempered instrument in an order of ascending fifths (C, G, D, A ...C) in which on th~ 12th step the initial key is reached again. (13, 101; [W. Apel, ed., Harvard Dictionary of Music, 2nd Ed. (Cambridge, Mass.: Harvard Univ. Press, 1969) pp. 171-172]) 1015. Color Xerox process (in reprography)-A machine process in which an original image in color is reproduced in full color on ordinary paper. The process differs from the 3-M process. (13, 129) (d. Term 1026: 3-M process) 1016. Cromalin film (in color printing)-Trade name for a sheet of photopolymer used to make a plastic printing plate. The film in contact with a photographic film positive is exposed to ultraviolet radiation. The radiation causes hardening of the polymer surface; the part of the surface shielded from the radiation is unchanged and remains sticky. Powdered 241 pigments dusted onto the exposed Cromalin film cling to the slightly sticky areas producing a colored image on it. The film is used as an expedient in the printing industry for the making of color proofs. (13, 131) (see term 1025: Photopolymer) 1017. Cusp (in geometry)-A point at which two branches of a curve meet and end, with a common tangent. (13,96; [3]) 1018. Gum bichromate printing (in photography)-(13, 131) (see Term 1019: Gum print process) 1019. Gum print process, gum bichromate printing (in photography)-An early photographic process in which a gum solution containing a pigment and a bichromate sensitizer is used in suspension. Only direct contact prints may be made by the process. (13, 130) 1020. Isomer (in chemistry)-A chemical compound having the same molecular formula as another but having different properties owing to a different arrangement of atoms within the molecule. (13, 99; [15]) 1021. Kirllan photography (in photography)-A method for making photographic images on ordinary photographic film and paper. In place of a light source, however, a device is employed to transfer an electrostatic charge onto an object to be photographed, and the charge on the object activates the photographic emulsion. (13, 129) 1022. Photo aluminium...