The Afazaruni Elver. Ii7 



From San-San-Kopai lainling to the landing at the mouth of the 

 Isenaru Creek, belonging to the Barnard Syndicate, the distance in a 

 straight line is about nineteen miles, the general direction of the river 

 being from the north-west. For about thirteen miles the course is 

 through quartz-porphyrite and porphyrites frecjuently more or less 

 schistose in character. Above this the river follows a very winding 

 ' course from Isenaru Creek, and the rocks are hornblende-granitite and 

 (juartz-diorite, while at the mouth of the creek a mass of coarse- 

 textured epidiorite is exposed. 



Above the junction of the Isenaru Creek with the Mazaruni River 

 the river flows through the lower shales of the sandstone formation, 

 and it enters on the sandstone proper at Peiniah Fall. 



About three miles up the Isenaru Creek, and for about a mile from 

 its right l)auk, the path leading to the Barnard Placers on the 

 Harimaraka Creek traverses shales and mudstones of the sandstone 

 formation. These are very similar in character to those seen in the 

 Cuyuni River and at Amatuk Falls in the Potaro River. Further 

 along the path are exposures of coarse-grained granitite, while at the 

 placers is a hill of mica-gabbro. 



7'Ae Puruni River. — The Puruni River flows into the Mazaruni 

 River on its left bank at a distance of about sixty-seven geographical 

 miles from Bartica. Compared with the latter it is a narrow river, 

 being about eighty yards across opposite to the Government Officers' 

 Station about a mile and a half from its mouth. The river pursues a 

 somewhat tortuous course from its mouth to the Mara-Mara Creek, 

 the general direction of its flow being from the north-north-west. 



The junction of the Puruni with the Mazaruni takes place at the 

 abrupt turn of the latter from the west near the Kurabiri Rapids. 

 "When the water in the Puruni is low its junction with the Mazaruni takes 

 place over a ridge of rocks running east and west across its mouth, 

 which gives rise to low cataracts or to small rapids according to the height 

 of the water. The ridge consi-ts of gneiss having tongues of diabase, 

 changed to proterobase and to epidiorite, intrusive through it. Many 

 exposures of gneiss — generally rather fine in texture, and in places 

 weathered into great slabs — are seen along its course from its mouth 

 to above the station. A little below the station the river is crossed 

 by a dyke of diabase, apparently abDut twenty-live feet in width, 

 trending to the north-north-east and south-south-west. 'J his dyke has 

 sent off-sets and narrow tongues into the neighbouring gneiss, as may 

 be seen in the rock ex})osed at the Government Officers' landing. 



Between the Puruari River, which flows into the Puruni River on 

 its left bank about a mile above the station, and the mouth of the 

 Puruni is a hill, about 500 feet high, consisting of medium to line- 

 textured diabase, which is in parts covered with great masses of 

 concretionary ironstone. Near the Puruari River the diabase o\'erlies 

 a banded coarse-textured hornblende-granitite-gneiss. Between the 

 station and Taparau landing, about 5 miles in a straight line to the 

 north-west of the former place, many exposures of granitite-gneiss 



