488 APPENDIX. No. VI. 



Capt. Tucke}', and affixed to one of them from the highest summit, informs 

 us that a globule of some metal, either gold or copper, has been seen adhering 

 to one of the cavities, by Dr. Smith ; but no such observation has been com- 

 municated in this Gentleman's jom-nal : the lump, however, bears evident 

 marks of having been exposed to the action of fire. There is scarcely any 

 appearance of metals in the rocks near the lower parts of the Zaire ; if, there- 

 fore, the accounts which the missionaries have ^ven of the great abundtmce 

 of every description of ores in Congo, extend to the banks of that river, it 

 must be higher up ; where, according to Dr. Smith's account, the rock-for- 

 mation appears to adopt a different character. The specimens from Condo- 

 Sono, Banza Nokki, and Benda consist of sienite, with gi-een hornblende, and 

 a rock composed of feldspar and quartz, with thickly-disseminated particles of 

 magnetic iron stone, instead of mica or hornblende. It Is probable that the 

 primitive trapp occurs here in beds subordinate to the gneiss and mica-slate, 

 of which a few specimens are sent, together with some others from the same 

 parts, which appear to be flint-slate. 



A rolled piece of sienite from the falls of Yellala, covered by a thin, 

 shining, black crust, proves, that the action of the y.ater of the Zau-e Is similar 

 in Its effects to that of the Oronoko. Thei-e are boulders of sienite In our 

 collection, found by Baron Humboldt, at the cataracts of Alures, which are 

 covered with exactly the same crust, and bear, externally, the most striking 

 resemblance to meteoric stones. This black crust, both in the stones from the 

 Zaire, and from the Oronoko, Mr. Children, to whom I communicated some 

 jiartlcles, found to be a mixture of oxides of iron and manganese. 



There are no specimens sent from above the Falls, except two varieties of 

 compact hmestone, one of them magnesiaft ; but the places from which they 

 came are not distinctly marked. 



This is all I have to say on the scanty materials before me ; and I leave It 

 to you to make any use of it you please. BeUeve me, my dear Sir, 



Your most obedient humble Servant, 



^ , , CHARLES KONIG. 



To John Barrow, Esq. Sec. to 



the Admiralty, &c. &c. &c. 



