state it is nearly as hard as wood, only just receiving the impression of the nail, is of a porous structure, and when viewed under the microscope has the appearance of a series of variously hued prisms. When moulded, rolled into sheets, or drawn into ropes, it assumes a fibrous character in the direction of its greatest length, in which direction consequently it can be stretched without rupture. If, however, a strip of a sheet be cut off across the fibre, it will be found that a redistribution of the tenacity of the slip takes place ; i.e., the direction of the fibrous character is developed in an opposite direc tion. The electrical properties of gutta percha were first noticed by Faraday. If a piece be subjected to friction, an electric spark can be obtained. On its relative electric conductivity, see vol. viii. p. 53.
At a temperature of 32 to 77 Fahr., gutta percha has as much tenacity as thick leather, though inelastic and less flexible. In water at 110 Fahr. it becomes less hard; towards 120 Fahr.^ it becomes doughy, though still tough ; and at from 145 to 150 it frows soft and pliable, allowing readily of being rolled and moulded. Q this state it has all the elasticity of caoutchouc, but this it loses as it cools, gradually becoming hard and rigid again, and retaining any form impressed on it whilst in its plastic condition. It is highly inflammable, and burns with a bright flame, dropping a black residue like sealing wax. The specific gravity of gutta percha has been variously stated at from 96285 to 99923. It is insoluble in water, alcohol, dilute acids, and alkalies, but dissolves in warm oil of turpentine, bisulphide of carbon, coal tar oil, caoutchin or oil of caoutchouc, and its own oil, for it yields by destructive distillation an oil similar to that yielded by caoutchouc under the same treatment. Ether and some of the essential oils render it pasty, and it is softened by hot water, absorbing a small quantity of the water, which is slowly parted with in cooling.
Manufacture and Applications.—Gutta percha, as received in England, is in irregular clumps or blocks, and is frequently adulterated with massive stones, sawdust, bark, sago flour, and other foreign matters ; and the first step in its manufacture is to cleanse it thoroughly. The blocks are first sliced by means of a. powerful circular wheel driven by machinery, and having fixed in it two or three strong chisel-like knives, by which it is divided into thin slices. These are placed in wooden troughs filled with water and heated by steam. As soon as the gutta percha becomes soft, it is taken out in baskets and placed in a toothed iron cylinder, called a "devilling" machine, which tears it into fragments ; these fall into a trough of water, and the impurities sink to the bottom, leaving the purified gutta floating in the form of a spongy mass. This mass is then taken out by means of perforated shovels, thoroughly washed in cold water, and dried in baskets. It is_ then packed in jacketed iron chests heated by steam, and left till it be comes soft, when it is at once removed, and kneaded or masticated by means of a cast-iron cylinder, with a movable lid and an internal revolving toothed iron axis, the result being a homogeneous dough-like reddish-brown mass. Sometimes various substances arc introduced into this machine, which is called a "masticator," to increase the hardness or density of the gutta, or to colour it, such as orange or red lead, chrome, vermilion, yellow ochre, sulphur, caoutchouc, gypsum, or resin, care being taken to use such sub stances only as are not affected by the heat necessary in the operation. The incorporation is conducted with great nicety, as at the will of the operator a soft and elastic or a hard and horny substance can be produced. When sufficiently masticated, the gutta is placed whilst still hot between two steel cylinders, and thoroughly rolled. _ By means of an endless band of felt the gutta is returned again to the cylinders, the distance between which is gradually diminished so as to compress and completely drive out any contained air from the gutta percha. There are various machines for cutting driving bands, &c. , to a uniform width, and for rounding off the edges and finishing. Soles for boots are made by cutting a long strip of the requisite width, and then passing the strip under a hollow die.
In making piping a machine is used consisting of a cylinder, with a die-piece attached of the requisite size. By means of a piston the gutta porcha, which is introduced into the cylinder in a plastic con dition, is drivfen through the die-piece, and the piston gives the inner diameter of the piping. As the piping issues from the machine, it passes immediately into a trough of water, which "sets" it, and prevents it from collapsing. The value of gutta percha piping is very great: it does not contaminate water as lead piping does; it withstands insects, damp, &c. , and is easily manipulated, being shortened, lengthened, or repaired without trouble or expense ; and its acoustic properties have led to its employment largely in the manufacture of aural, stethoscopical, and other instruments. Gutta percha speaking-tubes are now to be seen in nearly every office. The substance too, from the fact that few acids and alkalies affect it, especially if dilute, is largely employed for funnels, siphons, and other chemical apparatus.
In telegraphy gutta percha is of the very highest importance, being a cheap, lasting, and powerful insulator, easily applied to telegraphic wires. The general method of coating telegraphic wire is by charging a cylinder with plastic gutta percha, and forcing it through a die-piece, the wire forming a central core. As the wire 3 drawn through this "die" or "moulding" piece, it becomes oated to the requisite thickness, and after passing through water it is wound on drums ready to be coated with tarred rope, and with alvanized iron wire if required for submarine cables.
The readiness with which gutta percha, Avhilst in its plastic con dition, receives an impression, which it retains when cold, early led to its employment in the decorative and fine arts, since it repro duces the finest lines, as in the taking of moulds from electrotypes. See Electrometallurgy.
In the production of imitations of oak and other ornamental woods, gutta percha has been largely used, since by the admixture of various substances "graining" or ," marbling" can be very naturally represented, and a coating of a solution of gutta percha ives a varnish of great brilliancy.
Substitutes.—Many substances have been recommended as substi tutes for, or as supplementary to, gutta percha. Among these Balata gum undoubtedly holds the first place. It is obtained from the Mimusops Balata (Gartner), a tree found in British and French Guiana, Jamaica, &c. Prof. Bleekrod seems to have been the first to direct attention to this substance, by bringing it before the notice of the Society of Arts in 1857.[1] The Balata gum combines in some degree the elasticity of caoutchouc with the ductility of gutta percha, freely softening and becoming plastic, and being eatily moulded like gutta percha. What small parcels have been sent to England have met with a ready sale, and were remarkably pure and free from adulteration. But unfortunately, through the diffi culty of collection, the occupation being dangerous and unhealthy, the supply of this excellent article has fallen off. It is procured by making incisions in the bark of the tree about 7 feet from tho ground, a ring of clay being placed around to catch the milk as it exudes. A large tree is said to yield as much as 45 11) of "dry gum."[2] Pauchontee, the produce of Dichopsis clliptica, Collins (Bassia elliptica, Dalzell), is a most interesting substance, and may yet prove an article of commerce if properly treated ; at present, although by heat it becomes plastic and ductile, it is brittle and resin-like when cold. The tree is found very generally distributed in Wynaad, Coorg, Travancore, &c.
Many of the euphorbias yield milky juices which have some at least of the properties of gutta percha. The chief amongst these are the cattimandoo (Eiqrfiorbia Cattimandoo, Elliot) and the Indian spurge tree (E. Tirucalli, Linn.) of India, and some euphorbias at the Cape of Good Hope. The alstonia or pala gum (Alstonia sckc- laris, K. Br. ) and the mudar gum (Calatropis gigantea, B. Br.), have also been recommended as substitutes for gutta percha. But the at tempts made to utilize these substances have as yet been unsuccessful.
Future Supplies.—A very important matter for consideration is the question of the future supplies of gutta perchu. It is after all only a spontaneous natural product. If a Malay or Chinese wishes to plant pepper, gambier, &c., he burns down a portion of the forest, and when he has raised two or three crops he clears a new portion, and thus finely wooded spots become denuded of trees, and covered with rank grass rendering them unfit for further cultivation. Again, to obtain the gutta percha the trees are cut down, and none are planted in their stead, so that in districts where they were in abundance one or two only are now preserved as curiosities. It is a wonder indeed that a single tree is left. A writer in the Sarawak Gazette says that from 1854 to 1875 over 90,000 piculs (of 133J tt> each) of gutta percha was exported from Sarawak alone, and this meant the death of at least 3,000,000 trees. In fact the only thing that preserves tho tree at all is that it is of no use to cut one down till it is 25 to 30 years old. Sooner or later recourse must be had to cultivation and conservation.
(j. co.)
tinguished of modern German novelists and dramatists, was born 17th March 1811 at Berlin, where his father held a clerkship in the war office. After completing his education at the Friedrichswerder gymnasium, he entered upon the study of theology and philosophy at the university of his native town, where, having had his interest awakened by the political and social questions of the time by the Paris revolution of July 1830, he, while still a student, began his chequered literary career by the publication in 1831 of a periodical entitled Forum der Journalliteratur. Although, as was to be expected, the serial was a failure and was soon discontinued, it procured for him the notice of Wolfgang Menzel, who invited him to Stuttgart to assist him in the editorship of the Literaturblatt. At the same time he continued his university studies, first at Jena, then at Heidelberg, and latterly at Munich. In 1832 he published
anonymously at Hamburg Brief e eines Narren an eine
