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Rh the unprotected parts are hardened in proportion to the amount of protection they receive from the negative. After exposure under the negative the back of the film is exposed to the action of sunlight through the glass at its back, so that the whole film may be rendered as hard and tough and durable as possible to stand the wear and tear of the process of printing. When in its place in the printing press the film must be kept moistened. The soft parts unacted upon by the light, but from which the bichromate has been since washed, will absorb moisture in proportion to the action the light has exercised upon it, the absolutely hard parts refusing moisture altogether. The film may now be inked with an ordinary inking roller, the ink being freely taken up by the hard and unmoistened passages and by the partly hardened in proportion to the amount of moisture they are capable of absorbing; as in lithography, the constant moistening of the printing surface is a necessity. Collotype is largely used for postcards. It may be printed in a lithographic or ordinary vertical press of the letterpress printer. Admirable colour results are obtained by this process.

Heliotype is a variation of the method of producing the film which is first spread as described upon waxed glass and then stripped from the glass when dry. After hardening the back of the film it is laid down upon a metal plate and firmly secured to it by the use of an india-rubber cement. It is remarkable the admirable results that are obtainable by so delicate a process. The films have not a long life; a few hundreds only can be printed from each, but the renewal of the film is a simple matter. The result is very like a photograph. The use of heliotype is, however, practically obsolete.

Photolithography.—Zinc or aluminium plates are now frequently used instead of the more cumbrous stones for all so called lithographic printing. These plates have the same affinity for fat ink as stone, the method of dealing with them being practically the same as with stones, and the description may be taken as applying to both. The stone itself may be rendered sensitive by coating it with a thin film of bichromated gelatin, exposing it under a reversed negative of the required subject and treating the hardened film as it is treated in the case of collotype. A better plan is to render sensitive a sheet of unsized or transfer paper which is exposed under a negative, moistened, and rolled with transfer ink, which is of a specially fatty nature, and adheres only to the parts hardened by exposure which are unaffected by the moistening and remain dry. This inked sheet is laid upon the stone and the two together are subjected to great pressure, passing through a lithographic press. After further moistening the sheet of transfer paper is peeled off, the stone leaving the inked drawing behind it. The usual methods of lithography are then followed, the stone is treated with a preparation of acid and gum, kept moist and printed from in the ordinary lithographic method. Lithography of all kinds can only deal with lines or solid blocks. Tints present difficulties which are best dealt with by other methods of reproduction, but attempts have been made to obtain tints lithographically by breaking up the solid surfaces of the gelatin print with a grain before rolling it with ink and transferring it to the stone.

One of the most successful of such attempts is known as the Ink Photo process, which is more or less of a secret process worked by Messrs Sprague. None of them, however, yield so sound a result as a good drawing made in line, as the grain has a tendency to fill up. Transfers may also be made on to zinc plates which will take the lithographic ink equally well with stones. The plates may be etched—as the inked surfaces resist the action of acid—and by this means a relief plate made, which when mounted on a block, type-high, may be printed typographically. It is known in this form as zincography.

—Eugène Michel Chevreul, Considérations sur la reproduction par les procédés de M. Niepce de Saint Victor des images gravées dessinées on imprimées (Paris, 1847); Niepce de Saint Victor, Mémoire sur la gravure héliographique sur acier et sur verre (Batignolles, 1854); Niepce de Saint Victor, Traité pratique de la gravure héliographique sur acier et sur verre (Paris, 1856); Alexander de

Courcy Scott, On Photo-Zincography and other Photographic Processes employed at the Ordnance Survey Office, Southampton (London, 1862); G. Field, Chromatography (London, 1885); C. Motteroz, Essai sur les gravures chimiques en relief (Paris, 1871); Dr H. Vogel and J. R. Sawyer, Das photographische Pigment Verfahren oder der Kohledruck (Berlin); W. von Bezold, Theory of Colours, 1876; (Boston, U.S.A., 1891); J. Husnik, Das Gesammtgebiet des Lichtdrucks (Vienna, 1880, and editions); Ceymet, Traité pratique de phototypie (Paris, 1883, and editions); W. T. Wilkinson, Photo-Engraving on Zinc and Copper, in Line and Half-Tone (London, 1886); Alexander Leslie, The Practical Instructor of Photo-Engraving and Zinc-Etching Processes (New York, and editions); E. Leitze, Modern Heliographic Processes (New York, 1899); W. T. Wilkinson, Photo-Engraving (London, and editions); Professor Church, Colour (London, 1891); W. de W. Abney, Colour Measurement and Mixture (London, 1891); R. Meldola, The Chemistry of Photography (London, 1891); Colonel Waterhouse, Practical Notes on the Preparation of Drawings for Photographic Reproduction (London, 1890); Carl Schraubstaedler, Photo-Engraving; a Practical Treatise on the Production of Printing Blocks by Modern Photographic Methods (St Louis, U.S.A., 1892); Dr H. Vogel, The Chemistry of Light (London, 1892); S. R. Koehler, Museum of Fine Arts: a Catalogue of an Exhibition illustrating Reproduction Methods down to the Latest Times (Boston, U.S.A., 1892); Jules Adeline, Les Arts de reproduction vulgarisés (Paris); Sir J. Norman Lockyer, Studies in Spectrum Analysis (London, 1894); H. D. Farquhar, The Grammar of Photo-Engraving, trans. from the German (London); C. G. Zander, Photo-Trichromatic Printing (Leicester, 1896); H. W. Singer and William Strang, Etching, Engraving, and other Methods of Printing Pictures (London, 1897); W. Gamble, “The History of the Half-tone Dot,” (The Photographic Journal, Feb. 20, 1897); T. D. Bolas and others, A Handbook of Photography in Colours (London, 1900); W. de W. Abney, Photography. Penrose's Process Annual contains each year a list of the latest works dealing with the development and progress of mechanical photo processes. (Author:Edwin Bale)  PROCESS, in law, in the widest sense of the word, any means by which a court of justice gives effect to its authority. In the old practice of the English common law courts process was either original or judicial. Original process was a means of compelling a defendant to compliance with an original writ (see ). Judicial process was any compulsory proceeding rendered necessary after the appearance of the defendant. Process was also divided in civil matters into original, mesne and final. Original process in this sense was any means taken to compel the appearance of the defendant. A writ of summons is now the universal means in the High Court of Justice. Mesne process was either any proceeding against the defendant taken between the beginning and the end of the action, such as to compel him to give bail, or was directed to persons not parties to the action, such as jurors or witnesses. Arrest on mesne process was abolished in England by the Debtors Act 1869. Final process is practically coexistent with execution. In criminal matters process only applies where the defendant does not appear upon summons or otherwise. A warrant is now the usual form of such process.

Stet processus was a technical term used in old common law practice. It consisted of an-entry on the record by consent of the parties for a stay of proceedings. Since the Judicature Acts there has been no record, and the stet processus has disappeared with it.

In Scots law process is used in a much wider sense, almost equivalent to practice or procedure in English law. Where papers forming steps of a process are borrowed and not returned, the return of the borrowed process may be enforced by caption (attachment). The Scottish process is very much akin to the French dossier.

In the United States process is governed by numerous statutes, both of Congress and of the state legislatures. The law is founded upon the English common law.  PROCESSION (M. Eng., processioun, Fr., procession, Lat., processio, from procedere, to go forth, advance, proceed), in general, an organized body of people advancing in a formal or ceremonial manner. This definition covers a wide variety of such progresses: the medieval pageants, of which the Lord