Page:Encyclopædia Britannica, Ninth Edition, v. 12.djvu/868

842 842 I N D I N D very slightly greased. Before it is put in, the article is roughly put together, and the expansion of the included air forces the rubber into contact with the internal sur face of the mould, or a little carbonate of ammonia is en closed. Belting intended for driving machinery is built up of canvas which has been thoroughly frictioued with the soft mixed rubber, and is cured by placing it in a kind of press kept by means of steam at a dry heat of about 1 40 C. Packing for the stuffing boxes of steam engines is similarly prepared from strips of rubber and frictione-d canvas, as also are the so-called insertion sheets, in which layers of rubber alternate with canvas or even wire gauze. India- rubber stereotypes are now extensively made use of as hand stamps, and attempts have been made to introduce them for press and machine printing. A plaster cast of the type is, when dry, saturated with shellac varnish and redried. Rubber mixed in the usual way with about 10 per cent, of sulphur is now softened by heat, forced into the mould, and retained there by pressure during the operation of curing, which is usually effected in an iron box heated over a gas burner to 140 C. The ordinary macintosh or waterproof cloth is prepared by spreading on the textile fabric layer after layer of india- rubber paste or solution made with benzol or coal-naphtha. If cotton or linen is used, it is usual to incorporate sulphur with the paste, and to effect vulcanization by steam heat ; but, when silk or wool is employed, no sulphur is added to the paste, the dried coating of rubber being merely brought into momentary contact with the mixture of chloride of sulphur and carbon disulphicle already mentioned. Double texture goods are made by uniting the rubber surfaces of two pieces of the coated material. Air goods, such as cushions, beds, gas bags, and so forth, are made of textile fabrics which have been coated with mixed rubber either by the spreading process above described, or by means of heated rollers, the curing being then effected by steam heat. The manufacture of overshoes and fishing boots is an analogous process, only the canvas base is more thickly coated with a highly pigmented rubber of low quality. The articles are first fashioned by joining the soft material ; they are then varnished, and afterwards cured in ovens heated to about 135 C. The line vulcanized &quot;spread sheets &quot; are made by spreading layers of india-rubber solu tion, already charged with the requisite proportion of sulphur, on a textile base previously prepared with a mixture of paste, glue, and treacle. Vulcanization is then effected by steam heat, and, the preparation on the cloth being softened by water, the sheet of rubber is readily re moved. The required thickness of the spread sheet is very often secured by the rubber-faced surfaces of two cloths being united before curing. The threads used in making elastic webbing are usually cut from spread sheets. The manufacture of springs, valves, and washers does not re quire any very special notice, these articles being generally fashioned out of mixed rubber, and vulcanized either in moulds or in powdered French chalk. Hollers are made to adhere to their metal spindles by the intervention of a layer of ebonite, and after vulcanization they arc turned. In order to make spongy or porous rubber, some material is incorporated which will give off gas or vapour at the vulcanizing temperature, such as carbonate of ammonia, crystallized alum, and finely ground damp sawdust. TTncombined sulphur is injurious, and often leads to the decay of vulcanized goods ; but an excess, of sulphur is generally required in order to ensure perfect vulcanization. Sometimes the excess is partially removed by boiling the finished goods with a solution of caustic soda, or some other solvent of sulphur. In other cases the injurious effects of free sulphur are obviated by using instead of it a metallic sulphide. firenemllv the orance sulphide of antimony ; but, for the best results, it is necessary that this should contain from 20 to 30 per cent, of uncombined sulphur. When the vulcanization of rubber is carried too far say from the presence of a very large proportion of sulphur and an unduly long action of heat, the caoutchouc becomes hard, horn-like, and often black. Rubber hardened by over-vulcanization is largely manufactured under the name of ebonite or vulcanite. It is usually made by incorporat ing about 40 per cent, of sulphur with purified Borneo rubber by means of the usual mixing rollers, shaping the required articles out of the mass thus obtained, and heating for six, eight, or ten hours to from 135 to 150. Ebonite takes a fine polish, and is valuable to the electrician on account of its insulating properties, and to the chemist and photographer because vessels made of it are unaffected by most chemical reagents. A kind of vulcanite which contains a very large proportion of vermilion is used, under the name of dental rubber, for making artificial gums. The following list of works and papers on the rubber industry enumerates the writings which are calculated to be especially useful to the enquirer: Charles Goodyear, Gum Elastic and its Varieties, New Haven, U.S.A., 1853; Friedrich Harzer, G-utta-Percha und Kautschuk, ihr Vorkmnmen, &c., Weimar, 1853; Paul in Dcsor- meaux, Nouvcau manuel complet du fabricant d objets en caoutchouc, en gutta-percha, et en gomme factice, 424 pp., Paris, 1855; C. H. Schmidt, ])cr Fabricant von Kautschuk und Gutta-Pcrcha Waaren, 207pp., Weimar, 1856; Thomas Hancock, Origin and Progress of the Indian-It ubber Manufacture in England, London, 1857 ; Heinrich Keysserling s edition of Friedrich Harzer s Gutta-Percha und Kaut schuk, 273 pp. and atlas, Weimar, 1864; Abridgments of Specifica tions relating to the Preparation of India-Rubber and Gutta-Pcrcha, 1791-1866, 262 pp., printed by order of the Commissioners of Patents, London, 1875; &quot;India-Rubber and Gutta-Percha,&quot; a series of articles in the Universal, Engineer, vol. ii., Manchester, 1879; Franz Clouth, Die Kautschuk Industrie, 76 pp., Weimar, 1879; T. Bolas, Cantor Lectures on the India-Rubber and Gutta-Pcrcha Industries, London, 1880; M. Maigne, Noureau manuel complet du fabricant d objets en caoutchouc, &c., 2 vols., 506 pp., Paris, 1880. (T. 13.) INDICTMENT, in English law, is a formal accusation in writing, laid before a grand jury, and by them presented on oath to a court of competent jurisdiction. It is thus distinguished from a mere presentment by the grand jury made on information within their own knowledge, and from an INFORMATION (q.v.), by which a prosecution is instituted at the suggestion of a public officer without the intervention of a grand jury. The grand jury hears in private the witnesses in support of the application, and, if it considers that a prima facie case has been made out, it is its duty to find the indictment &quot;a true bill.&quot; Otherwise it sends the indictment into court torn up, which is a finding of &quot; no bill.&quot; In this case the indictment is said to be ignored. An indictment is said to consist of three parts the com mencement or caption, the statement of the facts constitut ing the ci line, and the conclusion. In each part appropriate and highly technical language is still used, but verbal pre cision is not so essential as it once was, and departure from the ordinary formalities, if it involves no misapprehension or mistake, does not make a flaw in the indictment. The formal commencement of an indictment is after the follow ing style : &quot;Middlesex to wit. The jurors for our lady the Queen on their oath present,&quot; c. The name of the county and district in the margin is the &quot; venue,&quot; and it should in general be the county in which the offence was committed, or the district over which the jurisdiction of the court extends. An indictment concludes with the words &quot; against the peace of our lady the Queen, her crown and dignity,&quot; if the offence is a crime at common law. If the offence is a crime by statute, the indictment must also use the words &quot; against the form of the statute in such case made and provided.&quot; In the &quot; statement &quot; great care must be taken to set forth the facts of the case with certainty