Page:Quarterly Journal of the Geological Society of London, vol. 27.djvu/576

 lowed by greenstone of a greyish hue, forming a dyke in a N.E. and S.W. direction, the rapids of Curanassai and a large gravel beach. Beyond this point were observed gneiss, hornblende, trachytes with iron pyrites, greenstone, a dark grey trap, quartzite followed by greenstone, schist, porphyry, and altered conglomerate.

At the mouth of the Carubung river there is a talcose slate, through which there are small veins of plumbago or graphite ; these are followed on the Carubung river by gneiss, greenstone, porphyry, granite, mica-schist, ironstone, conglomerate, sands, and clays. Several precipitous cliffs of stratified rock appear here above the forest, forming the Morokina, Wataparu, and Curumina mountains ; and the granite and metamorphic series of rocks are occasionally covered by large blocks of old conglomerate, composed of white quartz pebbles in a very hard siliceous matrix, which lie in the river at different angles of inclination. Soon after, the grey and pink granite disappear under extensive beds of conglomerate, composed entirely of siliceous rocks or quartz pebbles and boulders, coated, as all the rocks are in the rivers I have visited, by hydro-oxide of iron, with or without manganese. The falls of Macrabah are produced by a mass of this rock traversing the river 35 feet between the level of the water above and that below.

The hills on either side of this river, at the Macrabah falls, rise almost perpendicularly to the height of 1300 feet. To gain the summit, I proceeded up the Seronne, a smaller stream, and climbed up over large masses of conglomerate and sand until I attained that altitude.

By a slight divergence to the north of the Indian track a cascade may be seen, reported by Hillhouse to be 400 feet perpendicular ; it was dry when I passed.

On reaching the summit of that portion where the land becomes comparatively level, I found it to be, by aneroid barometer, 1500 feet, continuing to rise in a distance of ten miles to 2534 feet above the sea-level.

Nothing but sand (red, yellow, or white), ironstone, conglomerate, quartz -pebbles, as white as milk, and greenstone dykes is to be seen in the course of this transit.

On reaching the southern portion of this range I found it equally precipitous, and was obliged to descend by the aid of ropes tied to the trees that grew scantily out of the mural side of about 700 feet before reaching the level below.

The space between the base of the precipice and the Upper Mazuruni is occupied by rugged sand-hills cut by small streams into deep ravines.

The alluvial banks of this part of the Mazuruni present the same general aspect that they do below the great falls of Piamah, but become narrower on arriving at its junction with the Cako. On this part of the river granite was only observed at three points, under either the old conglomerate or recent alluvium.

From the mouth of the Carubung, during the journey up the Mazuruni, the rocks that appeared above the surface of the water