516 PROFESSOR J. W. GREGORY. 



contact of the older quartzites with granitic rocks, and those at Ochilesa are probably 

 due to water rising along a deep fault. The warmth of the water has aided the 

 growth along the upper part of the Quinie of the most tropical vegetation we saw 

 on the plateau, including palms 60 feet high, a dense undergrowth of ferns, and 

 numerous lianas. 



To the south of the Changa are some iron lodes which are the most extensive ore 

 deposits yet discovered on the Benguella plateau. I was unable to visit the main 

 ironstone lode, but examined some of the smaller ore masses to the west of it, at 

 some old native workings at Quimbundu. The lodes here strike on an average from 

 150° to 155°, and they are bounded by decomposed felspathic gneiss or schist con- 

 taining but little quartz. 



The ore occurs in lenticles, of which one that 1 measured is 13 yards wide 

 by 30 yards long, and its strike is to 28°. The country rock is a grayish schistose 

 felspar porphyry, and the strike of its foliation, where I observed it, varied between 

 150° and 165°. The country is cut through by north and south faults by which the 

 rocks have been greatly crushed. The leaching of the country rock along these 

 crushed bands has led to the segregation of the iron into lodes, lenticular ore bodies, 

 thin veins, and small scattered nodules of ore. 



On the bank of the Quime, near the mission station at Ochilesa, a light-gray gneiss 

 is interbedded with a blue non-foliated rock, which in the field I recorded as diorite. 

 Mr Tyrrell's miscroscopic examination shows it to be a dark-coloured hornblende- 

 hyperite and to be a member of the Charnockite Series. This rock includes many 

 inclusions of hornfels, which are no doubt altered fragments of sedimentary rocks ; 

 so that the Charnockite Series is apparently intrusive into the gneiss and schistose 

 quartzites. Dykes of shonkinite occur close by this exposure, but the vegetation 

 there concealed their relations. 



From Ochilesa we turned southward through the uppermost part of the valley of 

 the Cutato (Cuanza) to the watershed between the northern drainage and that to 

 the Zambesi. We began this march across the basin of the Changa and over the 

 pass to the west of the Iron Mountain. About 3 miles to the south of the pass, 

 beside a village whence Iron Mountain bears 10°, are good exposures of a white 

 felspathic schist interbedded with bands of a schistose quartzite composed wholly of 

 interlocking quartz. Beside this village were some deserted native iron workings. 



About a mile and a half to the south-south-east, on the banks of the Canji River, 

 is a light-coloured gneiss injected with granite veins ; and these intrusions may help 

 to explain the unusual strike of the rocks, which is to 153°. After crossing this 

 river we passed some large slag heaps of old iron workings and reached the Bui 

 River, beside which are extensive exposures of a gray gneiss containing biotite in 

 patches one inch long by half an inch thick. The strike here is 47°, with a steep dip 

 to the north-west. 



South of the Bui River is a plateau littered with schistose quartzites, including 



