424 PEOCBEDINGfS OF THE GEOLOGICAL SOCIETY. [May 24, 



to contain auriferous deposits as any other portion of it that I 

 have seen. 



The greatest elevation between the Cuyuni and Puruni rivers 

 was 320 feet, on the south of which a tributary of the Puruni 

 takes its rise. Down this narrow stream, we cut our way through 

 the branches and trunks of trees that were lying across it. After 

 passing the Tapara and the Tariparu creeks, from the south, granite 

 and syenite occur in two places, and after passing the Waini creek, 

 from the north, the river is divided into many branches by nume- 

 rous islands composed of a red clay, and obstructed by fallen trees, to 

 avoid which the Indians have cut a passage through the clay, large 

 enough for corrials (canoes) to pass. These clay banks are generally 

 low, and lie on some hornblende and schistose rocks near Maruparu 

 and again further down the river. 



Granite occurs near Tuvastimpi creek and a little belovr, associated 

 with gneiss of a blue colour. 



On approaching Curaspara creek a soft mica-schist occurs, near 

 which there is a hill of 600 feet elevation. The ascent is rather steep 

 being on the average 30° of inclination ; the trend is north-east, 

 and south-west. The surface is covered with hydro-oxide of iron, 

 in the form of pebbles, or in concretionary masses, sometimes con- 

 glomerated and hsematitic. 



Near the falls of Marchughi the hydro-oxide of iron occurs form- 

 ing a soft rock, with blackened surface. Diorite, trap, and green- 

 stone form the barrier across the river, about 15 feet higher than 

 the lower basin. A deposit of iron and manganese occurs on all the 

 rocks in this as in most of the other rivers in the colony. Some- 

 times I have seen it ^ of an inch thick. 



About a quarter of a mile below the junction of the Mapa-aima 

 with the Puruni, are the falls of Payuca, which are divided into three 

 streams. A dyke of greenstone forms the obstruction. The mica- 

 schist dips to the south-east. 



Ombaroa Creek enters the Puruni from the north a little below 

 these falls, and the hills of Euminga and Murupina soon appear, 

 forming the south bank. At the base of these hiUs are dykes 

 of a dense greenstone. Between these two hills is a small water- 

 course, near which I observed granite, syenite, trap, hornblende- 

 schist and decomposed schist. Near Gasparupa creek there is a 

 curious conglomerate, and also trap with quartz veins. After 

 passing Gangrooma and Langooma creeks greenstone occurs ; and 

 below Cabilli and Humaribara creeks quartz, greenstone, and con- 

 glomerate ; and at Paraani creek red and green schist with quartz 

 veins. These extend down to the vicinity of the Maramara creek, 

 where gneiss and blue clay-slate appear. A short distance lower 

 doAvn the river is a bed of conglomerate. 



The river soon after passes through a ridge trending north-east 

 and south-west, and soon after another hill is seen about the same 

 height (600 feet) trending more to the south. Then follows the 

 IJricon, which is the highest in the range. 



At the base of these hills a ferruginous conglomerate and red 



