292 PB. r. WELWITSCH ON THE GUM COPAL J>' ANGOLA. 



of Angola^ and their mercantile importance. — The shape in which 

 Grum Copal is found is very various : it often has the form of an 

 egg, a ball, or a drop ; at other times it looks like a flat pressed 

 cake ; and it is also met with in sharp-canted pieces. The pieces 

 of Grum Copal vary as mucli in size as in shape : they are rarely 

 larger than a hen's egg, and there are many much smaller ; others 

 (which, however, seldom occur) are as big as a man's fist, or even 

 a child's head, weighing three to four pounds and more. All the 

 pieces of Gum Copal of diflferent shape and size have one com- 

 mon characteristic, viz. that on their surface they are covered 

 with a thinner or thicker close-sticking, whitish, nearly chalky 

 crust, which exhibits on many pieces veins or network, whilst in 

 most instances it covers the surface like an earthy powder}^ coat. 

 The surface of fresh-broken pieces appears conchoidal, wuth finely 

 radiating lines in each conchoidal impression. The lustre is 

 glossy ; the mass is hard and transparent to a certain depth, and 

 where scratched wdth a knife or needle it leaves a white-pow- 

 dered stroke. It can easily be scraped with a knife into powder 

 which, if sprinkled over red-hot coals, changes instantaneously 

 into thick vapours, at first with a slight yellow colour, with a 

 strong aromatic smell, somewhat similar to that of incense. Large 

 pieces brought into contact with a light soon burn up, developing 

 at the same time the above-mentioned vapours. "When chewed, 

 it crackles between the teeth, without leaving a noticeable taste. 

 Whether Grum Copal has ever been subjected to a thorough che- 

 mical analysis I do not know ; but no notice or account of it is 

 given in the *Histoire des Drogues,' by Guibourd, in which 

 work are found the analyses of many East-Indian and American 

 Copal resins. The fact that there is often seen, even on the 

 canted broken sides of many pieces, the same bard, wbitish, 

 earthy crust which covers the other unbroken surface of the 

 same piece, tends to prove that after their falling oflf the mother 

 tree they were forcibly transported from their original spot by 

 floods or earth-falls, by which they were broken before they came 

 into the marl or sandy plains in which they are now found. At 

 times the crust just alluded to is very hard, of considerable thick- 

 ness, and with a glossy polish, which leads to the supposition 

 that pieces in which it is found have been imbedded for a 

 long time in the ground, or perhaps in water-basins. Whilst an 

 earthy crust of greater or less thickness is noticed on all pieces 

 of Gum Copal before it is washed or rubbed off, the colour m 

 different pieces varies very much ; some samples are yellowiwh- 



