146 TIiP Geoloiju of the Gold Fields of Jirifish Guiana. 



granitic — wliilst the freiiueut changes in direction result in the actual 

 course of the river l)eing above thirty miles. The first rocks seen are 

 about a mile to the north-west of the hornl^lende-schist, and consist of 

 (juartz-diorite, while above are many exjjosui-es of granitite, whilst the 

 banks of the I'iver show granitic decompositioji-products. About four 

 miles south-west of the exposures of (luartz-diorite the Merume River 

 joins the Mazaruni on its right bank, tlie Merume being about one 

 hundred yards wide at its mouth. 



Above the Junction of the Merume the course of the Mazaruni is from 

 the north-west by north for about eight miles, then curves to the south-east 

 for some two miles to the Kurekur Creek, from whence is a fine view of the 

 tSororieng Peak, thence it flows from the north-north-west for three miles, 

 and westward for a mile and half to near the mouth of the Mahwaiparu 

 Creek, the land being generally very low and swampy. East of the 

 Mahwaiparu Creek, at the foot of a low hill, an exposure of fine-grained 

 diabase occurs. Above this place the river Hows through low-lying land, 

 and fine views of the Kamukusa and Merume Mountains are seen, the 

 ranges being probably from ten to fifteen miles off from the right bank, 

 while in the far distance the Ayangkanna Mountains, a sandstone range 

 with characteristic precipitous sides and square tops, are visible. About 

 half a mile above a large forest-covered island near the northern end <jf 

 the curve, a broad dyke, about eighty yards wide, of diabase, trending 

 north-east and south-west, crosses the river. The rock of which the 

 dyke is composed is coarse in texture and light-grey in colour. The 

 river above this dyke flows from the westward, its course curving 

 at first somewhat to the north and later towards the south, and from 

 this reach fine views are obtained of the castellated peak of the Tomasing 

 Mountain, in elevation j^robably about three thousand feet. The granitite 

 terminates about halfway up this reach near the Tomasing Creek 

 mouth, where exposures of fine-grained diabase occur on the left l)ank. 

 West of here the river flows round a great, almost circular, curve for 

 a distance of seven miles, and along the curve exposures of quartz- 

 porphyrite and of felsite, more or less schistose in character, are 

 frequent, while at the end of the curve a mass of very coarse-grained 

 feldspathic diabase is seen. 



From here to 8an-San-Kopai landing, a distance of about fifreen 

 miles, the rocks seen are quartz-})orpli3'rite and felsite, intersected in 

 several places b}'' dykes of diabase. The first is situated at about 

 a mile above Aping Creek, where a dyke about twenty feet across of a 

 dark-coloured, almost black, dialiase of rather coarse texture strikes 

 north 15° east and south Id"-" west ; a second of a fine-grained 

 variety at Towabaru Creek strikes south 80" east anfl north, <S0° west, 

 and is about forty feet in width ; while about half a mile higher a 

 third trends in the same direction, and is about the same thickness. 

 At Kuribenang Island and Creek a large boss of medium to coarse- 

 textured diabase is exposed in places for about three hundred yards. 

 At about three miles below the San-San-Kopai landing, the Karabung, 

 a large river about one hundred yards in bi-eadth at its mouth, which 

 has its sources in the sandstone mountains on the right bank, flows 

 into the Mazaruni. 



