430 PKOCEBDINGS OF THE &EOIOGICAL SOCIETY. [May 24, 



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 diiference 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 Araa- 

 wak Indians and " Taquiari " by the Caribs, both signifying a large 

 water-jar. 



South of these hiUs 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 ofl' to the S.E. ; the summit is 

 comparatively level, resembling the sandstone mountains on the Ma- 

 zuruni 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. 



