Generally, the collection of guttapercha is carried on immediately after the rainy aeason ; in the dry season, the flow is very tardy, while during the rains, fever prevails, and the exudation is liable to be washed away. In Perak, no particular season seems to be recognized, and Murton was unable to learn whether the yield of the trees varies with the season ; but he is of opinion that in wet seasons the guttapercha must contain more water, and need mere boiling for its removal. The methods adopted for extracting the guttapercha vary somewhat amoug the Chinese, Malaya, and Dyaks. The mature trees are felled just above the buttresses, by tneans of axes wielded by men standing on a stage 14-IG ft. above the ground ; and the branches are immediately lopped off to prevent the sap ascending to the leaves. In Perak, the felling takes place at 5-6 ft. from the earth, and the top of the tree is also cut off at the point where it becomes too small for ringing. The ringing consists in making incisions in the bark of the felled trunk. The Binna people of the Alalay Peninsula cut the bark with a golo (small knife) or parang (bill-hook) at distances of 6-18 in. apart, around so mueli of the trunk as is accessible while lying on the ground, at the same time removing about 1 in. of the rough outer coating of the bark on each aide of the wnund, but without peeling off any of the inner bark. The Malaya of the same region strip off a ring of the soft bark about I in. wide in each ease. In some districts, the bark is beaten with mallets, to accelerate the flow of the sap. The latter exudes for shout an hour from each incision, and is caught pahn-leaves, coco-nut shells, and other receptacles, much, however, escaping to the ground and being lost. The extretne yields rnay be stated at 2 catties and 20 catties (of II lb.) per tree, the average being 3-5 catties. The differences in yield are not readily apparent, as the trees are usually about the same age. The crude juice, if in small qnantity, may be readily inspissated or concreted by rubbing between the hands. But this is rarely done, the rule being to boil the article in water in a kwali or iron pan about 15 itl. diam. and 6 in. deep, xvith the addition of various adulterants. The boiling is done partly for the purpose of driving off the water which usually gets mixed more or less with the juice, and gives a stringy and deteriorated appearance to the guttapercha. Arnong adulterants other than the juices of allied plants, one of the most irnportant is coce-nut-eil, to improve the appearance; lime-juice (1 pint to 3 gal.) has the property of coagulating the gutta pereha immediately on ebullition. Generally in Borneo some 20 per cent. of scraped balk is added; indeed, it is said that the Chinese traders, who buy up the gutta from the gatherers, would refuse the pure article in preference for that containing bark, te which the red colour is mainly due. On reaehing the export warehouses, the various kinds are assorted and sophisticated ready for commerce. The article is exported either in the form of balls weighing 13-20 catties (of IA lb.), or in large blocks, usually the latter for foreign ports.
The trade in guttapercha is of considerable end growing importance. Our imports of the raw article in 1880 were :—From the Straits Settlements, 62,862 cwt., value 50,5,821/. ; other countries, 2994 cw t., 22,0511.; total, 65,856 cwt., 527,872/., being an advance on previous years. Our imports from the Straits Settlements have increased from 19,665 ewt. in 1876, to 21,8s7 in 1877, 31,036 in 1878, and 49,387 in 1879. From Borneo direct, we received 22 cwt., value 350/., in 1876, bnt none is recorded since. The exports of guttaperoha and indiarubber combined from Borneo to Singapore in 1879 were valued at 437,027 dollars, or 91,047/. Tlae proportion from each Bornean port was :—Brunei, 27,720 dol. ; Labuan (received from the coast), 47,513 dol. ; Sarawak, 361,794 dol. Of the figure for Sarawak, guttapercha represents 320,507 dol., leaving only 41,287 dol. for indiarubber. The little port of Sandakan shipped 6277 dol. worth of guttapercha. The exports of guttapercha from Java for the year 1877-8 were 1113 piculs (of 135i. lb.) to Holland, and 6 to Singapore ; in 1878-9, 332 to Holland, 116 to Singapore, and 34 to England ; crop of 1879, 555 to Holland, and 274 to Singapore. It has been estimated that the shipments of guttapercha
from Sarawak alone during the years 1854-75 have totalled over 90,000 piculs (of 133-k lb.), iepresenting the destruction of at least 3 million trees. Our re-exports of guttapercha in 1880 were :-4524 cwt., 53,949/., to Germany ; 1796 cwt., 16,100/., to Holland ; 1137 cwt., 13,541/., to the T_Tnited States ; 1072 cwt., 4604/., to other conntries ; total, 8529 cwt., 88,194/.
The physical and chemical properties of guttapercha, and its industrial applications, have been described in a section of the article on Indiarubber Manufactures, pp. 1162-4. It may be added that while exposed to the air and alternations of temperature, it oxidizes aud decays rapidly, lasting only about 10 years on telegraph wires suspended in tunnels, but about 20 years when enclosed in iron pipes ; yet in the sea, 20 years' exposure produces no visible deterioration.
The approximate London market value of guttapercha is 6d.-3s. 6d. a lb. for genuine, and 3d.-2s. a lb. for re-boiled.
Guttashea.—This name has been conferred upon a substance, somewhat resembling gutta percha, found in appreciable proportion a per cent.) in shea-butter (see Oils and Fatty Substances, p. 1410). Beyond what is there stated concerning it, Dr. Letts, who experimented upon the substance for Thomas Bros., Bristol, obligingly writes as follows :—" I did not succeed in isolating from the gum any very defiaite product. To the best of my recollection, the portion soluble in ether separated gradually as an almost colourless solid, but I could not determine whether or no it was crystalline. I remember that I could get no definite salts or other compounds from either it or the insoluble residue. The only other fact I considered of importance was the odour which the gum evolved on dry distillation, whioh was exactly like that of indiarubber (when heated). This led me to think tbat the gum might be allied to caoutchouc." It has been separated in a manner to admit of its industrial utilization, but no application has yet been found for it.
Hardwickia balsam.—An important oleo-resin is obtained from Hardtoickia pinnata, a large tree, very common in the dense moist forests of the S. navancore ghats, and found also in S. Canara. The method adopted by the natives for extracting the balsam is parallel with that current in Brazil for procuring copaiba (see pp. 1639-40). The product is a thick, viscid fluid, bearing the closest likeness to copaiba, from which it may, however, be distinguished by the tests given on v. 1640. It is used medicinally in India as a most efficient substitute for copaiba.
See also Gurjuu, p. 1651.
Hog.—Tlae term "hog-gum " (which must not be confounded with the inferior tragacauth bearing the same name, see p. 1686) is applied in Jamaica to a yellow resin resembling Burgundy pitch in appearance, which escapes as a pelluoid juice from incisions in the trunk of Moronobea coccinea. It is used for making pitch plaisters and as a substitute for copaiba in Jamaica. In Brazil and Guiana, where it is known as mani or oanani, it is converted into torches, and employed. in pitcbing boats.
Indiarabber (FR., Caoutchouc ; GER., Ifautschuh).—The term " indiarubber," often and con veniently shortened to "rubber," is applied to a large class of inspissated plant-juices, chiefly yielded by the species named on pp. 1627-8. In England, the name " caoutchouc " is restricted to the hydrocarbon which constitutes the main ingredient of commercial rubbers. The plan on which the present article is framed is to commence with a description of the origin and production of the commercial rubbers in their alphabetic order—African (including Mozambique, Madagascar, Liberian, 8:c.); Assam, Java, Penang, and Rangoon ; Central American (including Cartagena, Guatemala, Guayaquil, Honduras, Mexican, Nicaragua, and W. Indies); Para ; Pernambuoo or Mangabeira—following with other kinds which as yet have no industrial importance, and con cluding with statistics of production, expoit, price, &c. The industrial applications of the rubbers have already been described in the article on Indiarubber Manufactures, pp. 1142-64.