De.scriji/he Geology. 109 



and three miles further up the river. A red oneissose granite occurs 

 below Wanaparu Creek, and in it intrusive veins of pinkish aplite occur. 

 A simihir aplite is seen in a grey gneiss opposite to Wanaparu Creek, 

 and again in red gneissose granite which the river traverses for about 

 four miles above the mouth of the Mehokowaina Creek, while an aplite 

 is intrusive in grey gneiss near Five Star Landing. The gneiss 

 near Wanaparu Creek is a hornl)lende-graiiitite-gneiss. About three 

 miles above the junction of the Mehokowaina Creek the red gneissose 

 granite is traversed by a white-spotted, dark-grey efjidiorite, which, in 

 places, shows a somewhat schistose structure. Similar more or less 

 schistose rocks traverse the grey gneiss and the gneissose granites 

 in many places between here and Five Star Landing. Some eight 

 miles below Carriage Falls, at a small rapid, a dyke of diorite, about 

 five feet in thickness, occurs in grey gneiss. The character of the 

 country is well shown by the fine-grained grey gneiss exposed at 

 Carriage Fall and at Hellgate Fall. 



In the neighbourhood of Five Star Creek and of Jimbo Landing 

 the rocks forming the hills consist of diorite and of epidiorite passing 

 to hornblende-schist. This structure of parts of the colony, as here 

 and in the Puruni Rivei* district, by degradation gives rise to payable 

 auriferous deposits. Some small diamonds have been found in the 

 placers of this district. 



The geology of the soui'ce of the Barima River, and of the Bariraa- 

 Barama divide, was described by Mr. Perkins as follows : — 



" The country at the Barima head is densely covered with forest 

 throughout, and is at an elevation ranging from 350 to 1,600 feet above 

 sea-level. The Barima has its source on the Imataka Mountains, which 

 are there some 950 feet high, composed of diabase and are highly 

 magnetic ; I believe they contain gold and other minerals, and I have 

 no doubt the various lines cut by the survey will be of use to pros- 

 pectors in traversing the district. At the head of the Kaliaku quartz- 

 porphyry occurs, and further along, at the source of the last consider- 

 able head of the Barama felsite is found. Hornblende-schist occurs in 

 many places, and many huge masses of quartz, which do not appear 

 to be auriferous, are found at intervals. These rocks are also notice- 

 able in the valleys of the streams flowing into British Guiana, whilst 

 on the Venezuelan side granitite and gneiss seem to be the characteristic 

 rocks. The mountain range with its spurs appears to be the result of 

 immense fissure eruptions through older formations of granite and 

 gneiss, and on the northern and eastern slopes the rocks in many 

 places lie exposed on a substratum of clay, derived from their decom- 

 position, while to the south the land is generally free from rock out- 

 crc>ps. The slope towards tne colony is nearly everywhere more abrupt 

 than towards Venezuela." 



The specimens collected from the Barima head, and from the high 

 land which forms the boundary between British Guiana and Venezuela, 

 are felsite, quartz-porphyry, and f eld spar-porphy rite of types common 

 in the colony. 



