Page:Encyclopædia Britannica, Ninth Edition, v. 12.djvu/864

838 838 I N D I A-R U B B E R artocarpacecms tree, with a trunk 3 feet or more in diameter, and large hairy oblong lanceolate leaves often 18 inches long and 7 inches wide, those subtending the young branches being much smaller and more ovate ( hg. 6). The tree grows most abundantly in a sporadic manner in the dense moist forests of the basin of the Rio San Juan, where the rain falls for nine months in the year. It prefers rich fertile soil on the banks of watercourses, but does not flourish in swamps. It is found also in Costa Rica, Guatemala, Honduras, Mexico, Cuba, and Hayti, and in Panama in company with another species, C. Mark- Jiamiana, Collins, and on the west coast of South America down to the slopes of Chimborazo, the Cordilleras of the Andes separating the Castilloce from the Hevece of Brazil, according to Mr R. Spruce. Nicaragua rubber. In Nicaragua the juice is collected in April, when the old leaves begin to fall and the new ones are appearing, during which time the milk is richest. The tree is tapped either in the same manner as the Hcvca, or by encircling the tree with a simple FIG. 6. Casii/loa elastica. a, young leaf (quarter real size) ; &, seeds (natural size); c, margin of leaf (enlarged) ; d, female flower and section of it (en larged). spiral cut at an inclination of 45, or by two spirals in opposite directions if the tree be large. At the bottom of the spiral an iron spout about 4 inches long is driven into the tree, and the milk is received in iron pails. A tree 20 to 30 feet high to its first branches, and about 4 feet in diameter, is expected to yield 20 gallons of milk, each gallon giving about 2 lb of rubber. In the evening the milk is strained through a wire sieve and transferred to barrels. The milk is coagulated by the addition of the juice of the &quot;achete&quot; plant (Ipomcca bona-nox, L. )or of another plant called &quot;coasso.&quot; The strained juice of either of these plants, obtained by bruising the moistened herb and subsequent expression, is added to the milk in the proportion of about 1 pint to the gallon. ]f these plants are not procurable, two parts of water are added to one of the milk, and themixture allowed to stand for twelve hours. The coagulum is next flattened out by a wooden or iron roller to get rid of the cavities con taining watery liquid, and the sheets are then hung up for fourteen days to dry, when they weigh about 2 It), the sheets being usually to ith inch thick and 20 inches in diameter. When coagulated by water, the mass is placed in vats in the ground and allowed to dry, this taking place in about a fortnight. It is then rolled into balls. That which dries on the incisions in the tree is called bola or burucha, and is said to be highly prized in New York. The loss of Nicaragua rubber in drying is estimated at 15 per cent. It is exported chiefly from San Juan del Norte, or Grey Town, and the larger proportion goes to the United States. The Castilloa appears to be suitable for cultivation only in districts where the Para rubber would grow equally well. The deciduous lateral shoots if planted will never grow erect. West Indian rubber is the variety usually imported into England, but in comparatively small quantity only. It occurs in the form of blocks, the finest quality consisting of thin separable sheets, and the second of &quot;scraps, &quot;usually conglomerated and containing frag ments of bark. It is the best description of Central American rubber known. It is not, as its name seems to imply, produced in the West Indies, but derives its appellation from being brought over in West Indian steamers. Honduras rubber rarely comes over to England ; it is of good quality, and free from &quot;tarry&quot; matter. Mexican rubber is imported into Liverpool in small quantity only. The imports of Mexican caoutchouc decreased from 1292 cwts. in 1875 to 158 cwts. in 1879. Guatemala rubber is a very inferior kind and very unequal in quality ; the best varieties are whitish, and the &quot;lower&quot; are black with a &quot;tarry&quot; appearance. It occurs in the form of sheets com pacted together, from between which when pressed a thick resinous fluid exudes. This when evaporated leaves a hard resinous sub stance unaffected by hot water or steam. The rubber is collected from the trees as in Nicaragua, but it is poured on mats to dry, and the thin sheets are subsequently peeled off, folded into squares, and subjected to pressure to remove as much as possible of the contained moisture. The imports of india-rubber into England from the whole of Central America amounted only to 2080 cwts. in 1879, having decreased from 5809 cwts. in 1875. The greater proportion of Central American rubber is exported to New York, especially that from Nicaragua and Panama. Siphocampylus Caoutchouc, Don., and S. Jamcsonianus, D. C., Central American plants belonging to the natural order Lobcliacece, are also stated to yield rubber of good quality ; and at the Phil adelphia exhibition a rubber called Durango caoutchouc, obtained from a composite plant, was exhibited. III. AFRICAN. India-rubber is produced throughout equatorial Africa, the chief districts of export being the Gaboon, Congo, and Benguela on the west coast, and Madagascar, Mozambique, and Mauritius on the east. The Madagascar, Mauritius, and Gaboon rubbers are, it is believed, chiefly exported to France. Those which enter into British commerce are known as Mozambique, Madagascar, and African, although the imports are described as coming from the following districts in the blue books : Senegambia and Sierra Leone 3808 cwts., West Coast 11,307 cwts., East Africa 7621 cwts., Cape of Good Hope 4241 cwts., Mauritius 570 cwts., Gold Coast 12 cwts. The above imports, which are for 1879, show an increase during the past five years, except in the case of Mauritius, Mada gascar, and the Gold Coast. Africa, in respect of the large amount exported, may now be considered as taking the second place as an india-rubber producing continent. Mozambique rubber, which is one of the most important varieties, occurs in the form of balls about the size of an orange, and &quot;sausages,&quot; or spindle-shaped pieces, made up of slender strings of rubber wound around a piece of wood, which i.s eventually removed ; or sometimes it occurs in smooth pieces of irregular size known as &quot; cake &quot; or &quot; liver.&quot; Madagascar rubber consists of two qualities, the best of a pink and the inferior or &quot;lower&quot; of a black colour, and occurs in shapeless pieces. The other kinds included under the general name of African are amorphous lumps called &quot;knuckles&quot; from Congo; small &quot;negro- heads&quot; or &quot;balls&quot; of scrap, and smooth cakes from Sierra Leone; small square pieces like dice called &quot;thimbles,&quot; and others more irregular in shape called &quot;nuts,&quot; and &quot;small negroheads&quot; from the Portuguese colonies; &quot;tongues,&quot; consisting of flat pieces, usually wet and sticky, from the Gaboon ; and balls &quot; from Liberia African rubber as a rule possesses more adhesiveness and less elas ticity than Para rubber, and is inferior in value. Comparatively little is known of the plants yielding caoutchouc in Africa or of the mode of collection. In Angola, according to Pr Welwitsch, the natives cither cut off a piece of bark, and allow the milky juice to run into a hole in the ground, or placing the hand against the trunk of the tree permit the milk to trickle down their arms, going from tree to tree until the arm is covered, when the rubber is rolled back towards the hand in the form of a ring. The wood of some of the trees, according to Mr Collins, contains a gum which, if the incision penetrates below the bark, mixes with the rubber and deteriorates it. In Madagascar, according to M. Coignet, rubber is obtained from the &quot;Voa-here&quot; or &quot; Voa-canja,&quot; Valica madagascaricnsis, Boj., the &quot; Voa-hinc, V. comorcnsis, Boj., and from V. gummifcra, Lam, In Senegambia it is obtained from the &quot;Anjouan,&quot; Vahca sene- galensis, A. I). C. In Mauritius Willuglibcia cdulis, Roxb. (which is found also in Madagascar, and in Chittagong and Silhet in India), appears to be the chief source of rubber. All the above are climb ing shrubs with opposite entire leaves and fleshy fruits. In Central Africa, from Liberia on the one side to Zanzibar 01 the other, caoutchouc is collected from plants of genera nearly allied