THE TROPICAL AGRICULTURIST. 



[July i, 1882. 



caoutchouc, but this it loses as it cools, graiiually 

 becoming hard and ri^id again, and retaining any 

 form impressed on it whilst in its jilaptic condition. 

 It is highly inflammable, and burns with a brigbt 

 flame, dropping a black residue like sealing wax. 

 The specific graviiy of gutta percha has been varionsly 

 stated at from 0-90285 to U-9ti923. It is insoluble 

 in water, alcohol, dilute acids, and alkalies, but 

 dissolves in warm oil of turpentine, bisulphide of 

 carbon, coal tar oil, caontchiu or oil of c.ioutchin, 

 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 ii is softened b}' hot water, 

 absorbing a email quantity of the water, which is 

 slowly parted with in cooling. 



Maiiufacture and Appliciil'wns. — 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 tir.-t 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 he- 

 comes solt it is taken out in baskets and placed in 

 a toothed iron cylinder, called a "devilling" maeliiue, 

 which tears it into fragments ; these fall into a trough 

 of water, and ihe impnriiies sink to the buttoui, 

 leaving the purified gutta floitiui< in the form of a 

 spongy mass. This mass is then taken out by means 

 of perforated slmvels, thoroughly washed in cool 

 water, and dried iu baskets. It is then jjacked in 

 jacketed iron chests heated by steam, and lefi till it 

 becomes soft, when it is at once removed, and kneaded 

 or masticated by means of a cast-iron cylinder, with 

 a movable lid and an iuternal revolving toothed iron 

 axis— the result being a homogeneous dough-like 

 reddish-brown mass. Sometimes various substances 

 are introduced into this machine, which is called a 

 "masticator," to iucrease the hardness or density of 

 the gutta, or to colour it -such as orange or red 

 lead, chrome, vermilion, yellow ochre, sulphur, caou- 

 tchouc, gypsum, or resiu, care being taken to use such 

 substances only as are not affected by the heat necess- 

 ary in the operation. The iucoriioration is conducted 

 with great nicety, as, at the will of the operator, a 

 soft and elastic or a hard and iiorny substance cm 

 be produced. When sufficiently masticated, the gutta 

 is placed whiht 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 riHjuisite width, and then passing the strip under 

 a hollow die. 



In making piping a machine is used consisting of 

 a cylinder, with a diepiece attached of the requisite 

 size. By means of a piston the gutta percha, which 

 is introduced into the cylinder in a plastic condition, 

 is driven through th" die-piece, and tlie piston gives 

 the inner diameter of the piping. As the piping 

 issu«s from the machine, it passes immediately into a 

 trou'di of water, which "sets" it and prevents it 

 from collapsing. The value of gutta percha piping 

 is very great : it does no'j cnntammate water as lead 

 pipinii does; it withstand'; insects, namp, &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, stethoscopioal, and other 

 instruments. (Jutta percha sptaking-tubes are now 

 to be seen in nearly every office. The substance too, 

 from tho 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 telegriiphic wire is by 

 chargi'g a cylinder with plastic gutta percha, and 

 forcing it through a die-piece, the wire forming a 

 ceuti-al core. As the wire is drawn through this 

 "die" or "moulding" piece, it becomes coated to the 

 requisite thickness, and, after passing through water, 

 it is wound on drums ready to be coated with tarred 

 rope, and with galvanized iron wire if required for 

 submarine cables. 



The readiness with which gutta percha, whilst in 

 its plastic condition, receives an impression, which 

 it retains when cold, early led to its employment in 

 the decorative and fine arts, since it reproduces tho 

 finest lines, as in the taking of moulds from electro- 

 types. See ELECTROMETALLUROy. 



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 "in,arb!ing" cun be very naturally represented, 

 and a coating of a solution of gutta percha gives a 

 varnish of great brilliancy. 



SitbstUutes. — Many substances have been recommend- 

 ed as substitutes for or as supplementary to, gutta 

 percha. Among these Balata gum undoubtedly holds 

 Ihe first place. It is obtained from the Mimusops 

 Bnliita (Gartner), a tree found iu British and French 

 Guiana, Jamaica, &c. Prof. Bleek rod 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. The Balata gum combines in some 

 degree the elasticity of caoutchouc with the ductility 

 of gutta perciia, freely softening and becoming plastic, 

 and being easily moulded like gutta percha. What 

 small parcels have been sent to England have met 

 with a ready sale, and were remarkably pure and 

 fri'C from adulteration. But unfortunately, through 

 the difficulty of collection, the occupation being dan- 

 gerous and unhealthy, the supply of this excellent 

 article has fallt-n ofl'. It is procured by making 

 incisions in the bark of the tree about 7 feet from 

 the 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 lb of "dry gum." Pititchontee, the 

 produce ol Dkhopsis ettiptica, Collins (Bnssia etlipika, 

 Dalzell), is a most interesting substance, and may 

 yet prove an article of commeice 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 iu Wynaad, 

 Coorg, Travaucore, &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 (Euphorbia 

 CaUimandoo, Elliot) and the Indian spurge tree 

 (E. Tirucallis Linn ) of India, aud some euphorbias 

 at the Cape of Good Hope. The alstonia or pala 

 gum (Ahtonia scholaris, R. Br.) and the mudar gum 

 (Galatropis-rj'Kjanlea, B. Br.), have also been recom- 

 mended as substitutes for gutta percha. But the 

 attempts made to utilize these substances have as yet 

 been unsuccessful. 



future SuppUen. — A very important mitter for con- 

 sideration is the question of tho future supplies of 

 giitta percha. 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 



