1871.] SAWKINS BEITISH GUIANA. 431 



From this no rocks appear above the surface until arriving at 

 " Musara," an abandoned Carib settlement ; and from this to King 

 William IV. Falls, a distance of five days from this point, there are 

 no rocks to be seen but granite, syenite, gneiss, a series of dense 

 hornblendic rocks, and in one instance columnar basalt. 



The Falls of King "William IV. consist of a succession of rapids 

 about 100 yards apart, closely interspersed with rocks. 



The Ascent of the Hupununi. 



The Rupununi river is one of the largest tributaries of the Esse- 

 quebo, entering it at nearly 4° N. latitude ; there is scarcely any 

 current perceptible at their junction ; and high banks of alluvium 

 occupy both sides of the river, which are sometimes broken by large 

 ponds or inlets, conveying the idea of an extensive depression be- 

 tween the Maccari and Paccarima ranges, and again between the 

 Makrapan and the Annai. 



The Makrapan Mountain is composed of granite and syenite. 

 From the base of this mountain] the great savannas spread to the 

 south and west into Brazil and Venezuela like large inland lakes, 

 a resemblance which is increased by the difi'erence of vegetation 

 growing on them. The alluvial deposits of the lower Essequebo are 

 covered by the largest and highest forests in the world, whereas on 

 approaching these savannas trees begin to decrease in altitude 

 until they become like the stunted growth on a promontory of a sea- 

 coast. This peculiarity is not confined to the river-courses ; for 

 the savannas or grassy plains are only here and there dotted by a 

 dwarf tree resembling the coast-grape, Ooccoloba uvifera. 



The geology of these savannas is very clearly defined, as they con- 

 sist of only three distinct, stratified Tertiary deposits, resulting from 

 the disintegration of the adjacent mountains : — 1st, sand, clays, and 

 vegetable mould ; 2nd, red sand and ferruginous gravel, often con- 

 creted or hsematitic ; 3rd, white clay, resting on gneiss, granite, &c. 



On the Annai mountains the savannas, or tracks of land denuded 

 of trees, rise to the summit in a most capricious manner in strips and 

 lines as regular as if laid down by line and compass ; but the rocks 

 do not difi'er in character from those on which forests grow. 



To the south of the Paccarima or Annai range are the Cunuku 

 mountains, which extend from the Takutu river on the west to the 

 upper Essequebo. This range is chiefly composed of granite and 

 gneiss, with trap dykes of the same character as those before de- 

 scribed. The savanna from the Eupununi to the Ireng and the 

 base of the Paccarima mountains consists of three Tertiary stratified 

 deposits. At the mouth of the Unamara river there is a vein of 

 quartz, and adjoining it are hiUs of quartz similar to those of Annai. 

 Between the savanna and the Unamara river there is a ridge of 

 granite intersected by greenstone dykes. 



The next hill to the northward is composed of a different kind of 

 rock, which continues to the edge of the sandstone escarpment on the 

 Sacaonta river. This rock in its commonest form is composed of 

 white crystals of felspar and clear crystals of quartz in a siliceous 



