Terminology

Leonardo, Vol. 10, p. 237. Pergamon Press 1977. Printed in Great Britain. T E R MINOLOGY The terms defined below were selected from artists' Articles and Notes published in the previous issue of Leonnrdo. Each definition is followed by an indication of the volume and page number of Leonnrdoon which the term first appears. The terms were not found in the art dictionaries among the dictionaries listed in Leonardo 10,63 (1977) 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. [ I I, 171, 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. 821. Collimator (in optics)-a device for producing a beam of parallel rays of light or of other radiation. (10, 99; [17]) 822. Colloidalchemistry-A subdivision of physical chemistry concerned with gels. emulsions. foams. etc.. in which substances are dispersed in the form of large groups of molecules. (10,127); [2,31) 823. Gyroscope (in mechanics)-A device that utilizes the angular momentum of a spinning mass to sense angular motion of its base about one or two axes perpendicular to the spin axis. Gyroscopes are used ;n the automatic controls of aircraft and spacecraft and in ship stabilizers. (10, 136);[W. H. Allen, ed., Dictionary o f Technical Termsfor Aerospace Use (Washington, D.C.: NASA, 1965)]) (cf. Terminology, Leonardo 9, 68 (1976): gyroscopicforce) 824. Halogen lamp (in electrical technology)-An incandescent lamp containing a tungsten filament, an inert gas and halogen vapour (e.g. iodine). The presence of halogen permits a cyclic process to occur by which evaporated tungsten particles are returned to the filament, and the inside walls of the bulb are kept free of the blackening effect of tungsten deposits. (10, 97) (cf. Terminology, Leonardo 1, 198 (1968): incandescent lamp; 4, 288 (1971): tungsten) 825. Metal painting-Term used by S. Buchanan for his wall reliefs that are made of metal parts, some of which are subsequently either painted, ground or polished. (10, 89) 8%. Organzine (in textile technology)-A fabric made from silk thread that consists of several filaments twisted together in the contrary direction to that in which the individual filaments were twisted. (10, 100;[16]) 827. Overhead projector-A device for projecting onto a vertical screen magnified images of graphic material on a transparency that is horizontally placed within the device and illuminated from below. (10, 103; [17]) 828. Periodic table (in chemistry)-An arrangement of chemical elements in the order of the number of protons in the nucleus. In such an arrangement, elements having similar properties occur at regular intervals and fall into groups of related elements. (10, 95) (cf. Term 831: proton, and Terminology, Leonardo 6, 261 (1973): element and nucleus) 829. Poly isobutyl methacrylate (in chemistry)-A synthetic polymer of isobutyl methacrylate. It is used in lacquer and varnish manufacture. (10, 127) 830. Poly n-butyl methacrylate (jn chemistry)-A synthetic polymer of n-butyl methacrylate. It isused in lacquer and varnish manufacture. (10, 127) 831. Proton (in physics)-One of the elementary particles of which the universe isconstructed. 11.is identical with the nucleus of the hydrogen atom and is a constituent of all other atomic nuclei. It carries a positivecharge that is numerically equal to the charge of an electron. [17] (cf. Terminology, Leonardo 6, 261 (1973): ntom and nudeus: 4, 288 (1971): electron) 832. Second-order-transition temperature (in physical chemistry )-A property of amorphous polymeric materials, for example certain plastics. It is the temperature below which the substance is in its glassy state, relatively hard and brittle, and above which it is in a state that approaches that of a highly viscousliquid.(lO, 128;[R. L. Feller, N. Stolow and E. Jones, On Picture Varnishes and Their Solvents, 2nd ed. (Cleveland: Case Western Reserve Univ., 1971) p. 1461) 237 ...