514 PROFESSOR J. W. GREGORY. 



gneiss. The strike of the foliation is to 68° ; and this rock is interstratified with 

 quartzites, quartz-schists, and sillimanite-schist, in all of which the foliation is nearly 

 vertical. The sillimamte is abundant in some layers, and the crystals are large 

 enough to be seen by the naked eye. Lower down this gully the gneiss is invaded 

 by a hornfelsed tonalite-porphyry (No. 159). 



The exposures at this locality show, as I had suspected from their general 

 character, that the schistose quartzites from the Ambussa Hills northward are a 

 much older series than the sandstones of the Oendolongo Mountains and near 

 Kalenga ; the quartzites of the Bailu-ndo district are quartz-schists and holocrystalline 

 Quartzites, and are interstratified in the lower Archean foundation. 



The route next day lay along the ridge that forms the watershed between the 

 Cuivo and the Lovule — the first tributary to the Cuanza. The chief rock seen is a 

 saccharoidal quartzite, which is often capped by an efflorescent ironstone that is 

 sometimes botryoidal. Some bands of a red chocolate soil indicate the deposition of 

 some basic rock. In the valley of the Lovule, 8 miles from our previous camp, 

 are bosses of dark bluish-gray biotite-gneiss, which encloses large blebs of quartz an 

 inch square, and is traversed by contorted quartz veins. Nearly a mile further on 

 are exposures of gneiss and felspathic quartzite ; further along the route are frequent 

 exposures of a dark-grey biotite-gneiss ; and the first main branch of the Lovule 

 River, a little west of the station of Catotlo, flows over sub-granulitic biotite-gneiss. 

 Around this station are further exposures of crystalline quartzites. Between Senhor 

 Leite's two stations of Catotlo and Chieuca is the upper part of the Lovule basin ; 

 the ground consists of series of flat-topped ridges between the valleys of the successive 

 tributaries. Exposures on the first part of the route are scanty, but the country 

 probably consists of schistose quartzite. At the bridge, about 12 miles north-east 

 of Catotlo, are outcrops of dark-blue gneiss. 



The higher ground to the east of this stream is littered with quartzite gravel, 

 and about 4 miles before reaching Chieuca is an exposure of the schistose quartz- 

 ites ; the foliation is nearly vertical, but with a slight inclination to the north, and 

 strikes from 50° to 56°. 



The station of Senhor Rodriguez Leite at Chieuca is on a high ridge of volcanic 

 rocks, which weather into a very rich red soil. The summit of the ridge to the 

 north of the station is composed of volcanic tuff and agglomerate. The general 

 aspect of these rocks and their freshness indicate that they are much younger than 

 most of the rocks of the Benguella plateau. Many of them show no signs of pressure, 

 and some of the lavas are still glassy. 



Mr Tyrrell has identified these rocks as shonkinite, sodalite-syenite, solvsbergite- 

 tull, and vitrophyre. Chieuca is a volcanic neck composed of alkaline lavas. From 

 Chieuca the ground descends steeply to a ford over the Cutato River, the gravels of 

 which consist of felspathic quartzite and gneiss. The rocks were not present in situ, 

 but the boulders on the stream bed are so angular that they cannot have travelled 



