Page:Quarterly Journal of the Geological Society of London, vol. 27.djvu/580

 vessel in which they preserve their favourite liquor " Paiwori ; " it resembles some of the rocking-stones.

After passing the still water in the depression mentioned I came to a succession of rapids rushing and pitching over beds of granite and dykes of trap that traversed the river, until I arrived above the falls of Itamine ; soon after the Taquiari mountains came into view, about 800 feet above the river.

This is the first place where I observed sandstone in situ ; dykes of greenstone pass through it, and rise on the south-east side of the Taquiari. At the termination of the hill, about 600 feet above the river, a column of rock stands out from a somewhat similar one, which makes the final point on the hill. This has weathered into three distinct pieces of rock, resting on a broad base one above the other. At each junction there is a separation ; and as at these junctions the weathering of the rock has been greatest, each piece has assumed a spherical or elliptic form ; and as the difference in size of the three is proportionate to the form of the large water- vessel used by the natives, the name " Comuti " has been given to it by the Araawak Indians and " Taquiari " by the Caribs, both signifying a large water-jar.

South of these hills there is a great depression or extent of level land towards the south-east, corresponding to that I observed at the upper part of the Demerara river. The banks of this river are low : and, I suppose, by a rise of ten feet above the present level it would overflow its banks. Before reaching the large pond of Tambicabo I observed some altered sandstone in the middle of the river, the granular structure of which is nearly obliterated, making it appear like flint : it decomposes into white sand.

The Tarratara hills are seen in the distance ; the land around them is low, extending apparently many miles back from the river. At the falls of Ouropocari there are some very curiously water- worn rocks ; parts of them are porphyritic, and others like an altered conglomerate. They are deeply grooved by weathering ; some rest on others of very inferior size, leaving space beneath them to shelter many men.

After passing over a series of rapids and cataracts formed by dykes of trap and porphyritic rocks, the Macari Mountain is seen, with a mural precipitous escarpment of near 1000 feet above the river. The range appears to trend off to the S.E. ; the summit is comparatively level, resembling the sandstone mountains on the Mazuruni river ; and it appears to have been cut away by the Essequebo river, but resembles more the cliff of a sea-coast. At the base there are dykes of a purple-coloured porphyry.

At the Pishani falls the rocks present the character of altered sandstone. At the upper part of the falls these rocks are of much finer grain.

On the east side of the river, granite rises to the surface and covers a considerable area, particularly at the cataract of Achramucra. From this the river rises but little, as it becomes comparatively still water.