Of GUIANA, 51 



hills more inland, and as far as we could examine them, of the 

 fame materials. The granite was both of the red and the gray 

 kinds, but chiefly of the latter. A number of feams or dikes 

 crolTed it here and there in all diredlions, not diftindlly fepa- 

 rate, but firmly united to the reft, making as it were but 

 one body with it, and confifting of the fame materials diffe- 

 rently modified. Their component parts were generally fmail- 

 er ; they were more compacft and clofer in the texture than 

 what furrounded them ; and where they had been equally ex- 

 pofed to the action of the weather, they appeared to have born 

 it much better than the furrounding granite. The origin of 

 the fand was now accounted for. This ftone, in fome cafes ex- 

 ceedingly firm and durable, is in others very liable to decay ; 

 and the wafli of thefe enormous chains of hills was able to fur- 

 nifh abundance of fuch fand as we had met with below. The 

 granite afforded many varieties, indeed every fliade, from large 

 and diflincft grained, to that whofe component parts of felt- 

 fpar, fchorl or quartz, were fo fmall as to refemble pretty com- 

 pact, compound lavas, or fome of our mixed whin-ftones in 

 Scotland. All thefe varieties would be found at no great di- 

 ftance from each other. I brought fome fpecimens, from Ti- 

 ger's berg, a hill about 500 feet perpendicular height, which 

 have every appearance of having undergone the adlion of fire. 

 They refemble half-vitrified fcorije, and would be taken for 

 them, but that they were adlually broken off from the granite, 

 and difcover all its parts in the fradlure. The fummit of this 

 hill is irregular, with feveral pits and holes among the rocks. 

 A little higher than it, and I fuppofe nearly about 200 miles 

 from the fea, you meet what are called the Falls. They are 

 only five or fix rapids, within the fpace of a mile or two, form- 

 ed by ledges of very clofe-grained gray granite that run acrofs 

 the river. There are breaks in each of them, through which 

 the dextrous Indians are able, in their light canoes, to pafs up 

 at any feafon, even the dried ; and when the river is fwelled by 



G 2 the 



