PRI 



591 PR I 



synonymous with axiom, and in the lattor 



it is an established principle. 2. The 



term is vaguely used in chemistry. It 

 sometimes denotes a component part, as 

 the constituent principles of bodies. At 

 other times it means a substance, on the 

 presence of which certain qualities, com- 

 mon to a number of bodies, depend : thus 

 we say the acidifying principle. We have 

 also proximate principles of animal and 

 Vegetable bodies, meaning thereby sub- 

 stances peculiar to those bodies, which 

 result from peculiar modes of combina- 

 tion of ordinary matter. 



PRINT'ING. The art of taking copies by 

 impression of type, engraved plates, and 

 blocks, or any design or work whatever, 

 in black ink, or pigments of various 

 colours ; but the word printing, without 

 any distinctive addition, is usually under- 

 stood to imply typography, or printing 

 from type, usually called letter-press print- 

 ing. The art is divided into two depart- 

 ments, composition, or the arrangement 

 of the types ; and press-work, or the taking 

 off impressions from the types so ar- 

 ranged : the workmen employed are 

 therefore distinguished into two classes 

 compositors and pressmeti. 



PRINT'ING-INK. A composition, accord- 

 ing to Mr. Savage's recipe, of balsam of 

 capivi (36), lamp-black (12), indigo and 

 Prussian-blue (together, p. aeq. S.I.Indian- 

 red (3), turpentine soap (dry 3). This 

 gives a superfine black ink : the pig- 

 ments for the coloureS inks are carmine, 

 lakes, vermilion, red-lead, gall-stone, 

 Roman-ochre, yellow-ochre, verdigris, 

 blues and yellows mixed for greens, indi- 

 go, Prussian-blue, Antwerp-blue, lustre, 

 umbre, sepia, Venetian-red, &c. 



PRINT'ING-MACHINE. A general name 

 for all self-acting printing-presses. The 

 first machine of this sort was projected 

 by Mr. William Nicholson, (1790); but 

 the first operative machine of the sort 

 was contrived by, and constructed under 

 the direction of, Mr. T. Konig, a clock- 

 maker from Saxony, (1804). This formed 

 a basis for the admirable machine of 

 Messrs. Cowper and Applegarth, first 

 constructed for printing the Timet news- 

 paper, and which is capable of thro wing off 

 4200 copies per hour of that large paper. 



PRINT'ISG-PRESS. The common ap- 



paratus employed in taking impression 

 from types. 



PR ION 'TES. A genus of passerine birds : 

 the Motmots. Family Tenuirostres. They 

 are beautiful birds, as large as the mag- 

 pie : fly badly, are solitary, build in holes, 

 and feed on insects. 



PRI'OR (Latin). 1. The first in the order 

 of time. 2. The superior of a convent. 



PRI'SAGE, Fr. prise, from priser, to 

 prize. See BUTLERAGE. 



PRISCII/LIA.NISTS. A Christian sect, so 

 denominated from Priscillian, bishop of 

 Avila, who practised magic, maintained 

 the errors of the Manichees, and held it 

 to be lawful to make false oaths in sup- 

 port of one's cause and interest. 



PRISM, Gr. tr^if/jM, from jrg<aj, to cut. 

 1. A solid, whose bases or ends are any 

 similar equal and parallel plane figures, 

 and whose sides are parallelograms. They 

 receive particular names from the figure 

 of their bases, as triangular, square, 



pentagonal, hexagonal, &c. 2. In optics, 



a triangular 

 prism of glass, 

 which sepa- 

 rates the rays 

 of light pass- 

 ing through it, in consequence of the dif- 

 ferent degrees of refrangibility that take 

 place in different parts of the same ray. 



PRISMAT'IC COLOURS. The colours ma- 

 nifested by the decomposition of a ray of 

 light in passing through a glass prism. 

 These are violet, indigo, blue, green, 

 yellow, orange, and red. 



