At the end of the rainy season, the copal is usually carried ungarbled to Zanzibar. Hence, after being sifted and freed from foreig-n rnatters, it is sent by the Banyan rttailer to the Indian market, or sold to the foreign merchant. It is usual also to effect the " cleaning " here, though this is also done at Bombay, in some European ports, and notably at Salem, in Massachusetts. It is performed in the following manner :—The resin is first washed in a dilute alkaline ley, hy which it loses some 20-37 per cent. of its bulk ; it is then aun-dried for some hours, and subjected to a brushing suffi ciently hard to remove the outer coat, but not to injure the goose-skin. The dark "eyes " where the dirt bas suuk deep are picked out by an iron tool. The next atop is garbling, which is done with careful regard to colour and size, and requires great experience. As a rule, the clear and aemi-transparent pieces are the best ; then follow the numerous and almost imperceptible grades of dull-white, lemon-yellow, amber-yellow, rhubarb-yellow, bright-red, dull-red, blackish, and gmss green. In size, the pieces vary from that of small pebbles tu t-3 oz. ; they have been known to weigh 5 and even 35 lb. Finally, the gum is put into boxes for export. The dust, of which perhaps 30 lb. daily is brushed off by each workman, is termed " sand," and cast away as of no value; it is probably genuine resin, and of some worth.
The commerce in E. African copal is extensive. Zanzibar exports sorne 800,000-1,200,000 lb. annually, of which, 150,000 lb. goes to Hamburg, and about 2 lacs' (say 20,0000 worth to Bombay. The Bombay imports in 1872-3 were 966 cwt. from the African coast ; the exports were 312 cwt. to the United Kingdom, besides 48 cwt. chiefly to the Persian Gulf, Straits Settlements, and China, and 211 cwt. to the other presidencies of India. The exports of copal in British ships from the E. coast of 1VIadagaacar in 1872 were valued at 3166/.
On the W. coast of Aftica, which is still richer in copal than the S.-E. coast, this resin is dug over a coast length exceeding 700 geogr. miles, between lats. 8° N. and 14° S. The copal is here found in a auperficial stratum of marl, sand, and clay, at a depth varying up to 10 ft. The most important copal districts of W. Africa are Sierra Leone (N. part), Accra, Benin, Gaboon, Loango, Congo, Angola, and Benguela (S. part). Of the Angola product, Monteiro says that it comes almost entirely from the Mossulo country, though it exists further north, as at lllangue Grande.
The botanical sources of W. African copal are scarcely determined with certainty. Daniell attributes the Sierra Leone article to Guibourtia copallifera, and perhaps some other species ; but Wel witsch is unable to state positively the origin of the copal of Angola and Benguela. The W.
African copal, like that of the S.-E. coast, occurs as a recent fossil. Its existence iu the most recent formations, and the water-rolled form of the fragments of Sierra Leone copal found between the rivers Pongas and Malaenzi, render it probable that the trees which afforded, and perhaps atill afford, copal do not belong to the coast flora, but to tbe interior, whence the resin has been trans ported by the rains and rivers. Monteiro saya that, according to native accounts, tbe Angola copal is found below the surfitce of a highly ferruginous hard clay, at a depth of a few in. to 2 ft.; it probably extends much deeper, but the natives are too lazy to look for it. It is dug for during and after the last and heaviest rains, in March-lVlay, no trees and but little grass growing above the spots where it is sought for. The resin is collected by the negrocs, who at the same time gather dye-plants and gurus, with the latter of which, no small quantity of copal is surreptitiously mixed. The copals of the Gaboon and Loango figure chiefly in French cornmerce ; the large masses Flom Angola, Benguela, and the Congo go principally to N. America, and in minor quantities to Lisbon and other European ports. The total exports are estimated at about 2 million lb. annually.
The copals of N. and S. Guinea exhibit very distinct differences. Those of the former are divided into 2 kinds, known as " young and pebble copals of Sierra Leone." To the latter, belong the °opals of Angola, Benguela, and the Congo. These three are so much alike that they aro always placed together, and are known simply as " Angola." The copals of Gaboon and Loaugo aro quite distinct again.
The " young copal of Sierra Leone " is said by Daniell to be derived from the living stems of Guibuartia copallifera. It consists of globular or tear-like pieces 4-1 in. diam., sp. gr. 1.06, of about the same hardness as S. American e,opal (Jutahy-seca), and of similar commercial value. It is °unearned chiefly in England.
The " pebble copal of Sierra Leone " is in small pebbles 1-1 in. diam., colourless or white to yellowish, homogeneous, translucent to transparent, with rough exterior, and occasionally covered with an opaque crust of the thickness of paper. It is quite odourless and flavourless, is the hardest of all the W. African e,opals, and has a sp. gr. of 1.09.
Gaboon copal occurs in round, flattened pieces 4-2i in. diam. ; the surface is mostly smooth, but is sometimee covered with a crust of branch), striations. The grains are wine-yellow, lees transparent and less homogeneous than the foregoing kind; their sp. gr. is 1.073. The fracture is conchoidal to splintery, and of glassy lustre when fresh. The scratch-line on newly fractured surfaces is smooth ; on older surfaces, splintery.