1871.] SAWKINS BKITISH GXTIANA. 425 



clays are found accumulated on either granite or some hornblende 

 rock. 



Kear the Tacuparu creek a decomposed granite appears, also at 

 the rapids of Maritote, and others below them, where the granite 

 and syenite are extensively exposed. 



After passing several rapids, including that of Alabamaloo, the 

 syenite is more general, A remarkable dyke of porphyry, 4 feet 

 wide, which has passed through the granite, occurs at the falls, 

 which were about 12 feet in height at the time I descended. 



The granite series, with trap dykes, are more largely developed. 

 At Huamata they cross the entire river. Most of this granite is 

 very coarse-grained, with green or red felspar. 



At the rapids and the island of Taparu, also at the rapids of 

 Presatu, white granite occurs ; and near Cubangan, gneiss, which 

 extends down to the Ourasas-sartur rapids. 



The land rises here, on each side of the river, to from 150 to 200 

 feet. At the base granite, syenite, trap, and quartzose rocks spread 

 out over a much larger surface, in comparison with those on the upper 

 part of this river. 



After passing the great falls at the junction of the Puruni with 

 the Mazuruni, there is so great an extent of bare granite separated 

 into innumerable islands, and such a large expanse of water within 

 the low and distant confines of the river, that it presents a scene 

 rarely to be met with. 



On entering the Mazuruni I found the river unusually low, and 

 consequently many rocks exposed that would not have been seen had 

 the river been in flood ; but all are so uniform in their character 

 (granite, syenite, gneiss, and porphyry, with trap dykes) as to 

 render the labours of the geologist very monotonous. 



These rocks continue up the river without any important modi- 

 fi.cation as far as the Wanamu and Maribisi rivers, where a fine 

 conglomerate occurs. Above this there is an altered sedimentary rock, 

 forming a mass. 



At the falls of Tebuco there are granite, diorite, and very dark 

 porphyry, also veins of dark quartzite, followed by greenstone, and 

 schistose rock with quartz veins, both black and white. 



At Carinang Creek the same rocks occur, and continue some 

 distance further up the river. Some of the quartz veins are bold, 

 being several feet across ; but no gold could be detected in them with 

 the aid of a strong magnifying power. 



About this part of the river I obtained the first view of the 

 Maribiacru cliffs, which form a part of the Mereme range, rising 

 from 1000 to 2000 feet over the forest-trees growing on the banks 

 of the river. 



At a point turning south, towards the cliffs, granite underlies 8 

 and 10 feet of recent conglomerate and sand interstratified ; then the 

 granite again rises to the surface. 



At this point the heights of Caribisi are seen to rise in a peak 

 about 18 to 20 miles distant ; and not far above, conglomerate is 

 a"'ain seen lying on white granite with quartz veins. This is fol- 



