G. ATTWOOD ON SOUTH-AMERICAN GEOLOGY. 585 
The mountain-pass cver Mafio Piedra is 1441 feet in height. 
Granite continues for about five miles, when a dike of basalt about 
one mile in breadth is found on the §.E. side of the mountain. Near 
the base of the mountain quartz breccia is again met with, and is 
about two miles in width, and of a similar character to that found 
at the N.W. base. A schistose granite is now found consisting 
of white quartz, felspar, and mica. At the farmhouse of La 
Florida (see Map) a stratum of slate-rock of a reddish colour, mode- 
rately weathered, but much altered, crops up, having an east and 
west strike, and dipping nearly vertical, but having, if any thing, a 
slight inclination to the south. Near the above is found a large 
quartz vein, containing pyrite, which is often decomposed. No 
minerals of value have been found in it so far. Proceeding still in 
a §.K. direction, the rock is again found to be granite, but having a 
schistose character. Large veins of quartz resembling reefs are 
found about every half-mile, and the quartz fragments are scat- 
tered to such a great extent over the hills and valleys that travelling, 
even on foot or on horseback, becomes tedious as well as dangerous. 
The country is now more open, very few large trees are met with, 
and but little vegetation is seen. 
Granite still continues. 
Upon reaching the Carichapo river close to the farmhouse called 
Candelaria (see Map and section), a belt of coarse slaty rocks about 
one mile in thickness is found cropping out, having an E. and W. 
strike and a slight dip to the 8S. From Candelaria to a farmhouse 
called Platanal, a distance of about twenty-four miles, a greyish- 
white granite prevails, and in it are numerous quartz veins. At 
present none of them have been found to contain any of the precious 
metals. 
For about one half the latter distance the road goes through the 
forest. Leaving Platanal(961 feet above sea-level) the greyish-white 
granite is still found, and continues until the farm of Cunuri is 
reached. 
Cunuri is 783 feet above sea-level, and is distant about twelve 
miles from Platanal. The road has a gradual descent from the latter 
place over an open rolling country composed of granite, in which 
barren quartz veins are numerous. Near Cunuri a small belt of 
mica-schist is found dipping nearly vertical, and having an KE. and 
W. strike. A small belt of gneiss is now met with. Adjoining it 
is a narrow belt of quartzite of a highly indurated, saccharoidal 
character. 
From Cunuri to the old Jesuit mission village called Quacipati 
the same greyish-white granite is the predominant rock ; but about 
a quarter of a mile on the N.W. side of the town granite disappears 
and a fine-grained gneiss takes its place. It contained silica 72°50 
per cent. About one mile to the 8.K. of Quacipati, granite reappears 
and continues to the Yuruari river. The Yuruari is one of the 
main branches of the Essequibo river, which empties itself into the 
Atlantic Ocean near Georgetown, Demerara (British Guayana). On 
each side of the river (Yuruari) is found a stratum of coarse slaty. 
