1008 The Naturalist Brazilian Expedition. [Oct 
above the river, but it is generally much lower. Succeeding this 
is an irregular swampy valley, two or three miles wide; then 
several small streams, branches of the Arroio da Divisa, whi 
cut through this ridge from south to north. The fourth ridge, 
which immediately follows, is rugged and almost mountainous in — 
its character, and higher than any of the preceding. It is fol- 
lowed by a wide, deep valley, on the southern side of whichis — 
the fifth ridge, properly the eastern end of the Serra do Herval, 
which at this point is probably 2400 feet above the Jacuhy. 
All of these ridges are composed of massive red granite, either 
coarse or fine. It is intersected here and there by quartz veins, 
varying in thickness froma few inches to many hundred feet. 
Commonly these veins appear as little ridges on the surface; 
larger ones form long hills, as may be seen just south of | 
Arroio dos Ratos, on the road to Dous Passaros. The qua 
varies from translucent to white or granular. ee: 
Above the granite in some places are layers of gneiss and 
mica schist. These are well seen in the beds of streams betweet 
the third and fourth ridges which I have described, about fi z 
miles south of the Arroio dos Ratos. Here the layers are v 
much twisted and distorted, but the stratification is quite eR 
Most of the layers are rich in mica, breaking with a schist 
fracture, but some are massive, resembling the gray gneiss of Rio 
de Janeiro. It is difficult to determine the strike, but this af 
_ pears to be nearly E. W., corresponding to the trend of the gra? 
ite ridges; some of the folds are perpendicular or reversed i 
did not see them in contact with the granite, but they are appa 
rently uncomformable. Gneiss is also seen south of the 
ridge, in the bed of a stream; here it is massive, an¢ I sa 
signs of mica schist. a 
Overlying granite and gneiss, but seen only in the hollows 9® 
d rocks, 
tween the ridges, are layers of stratified and unaltere 
forming the third great system seen here. In the Sao J ba 
district these beds appear in three portions or basins; first, the 
tween the Rio Jacuhy and the first ridge; second, betun o 
first and second ridges ; third, between the fourth and fifth r105 
just north of the Serra do Herval. The strike varies from 
