354 Quaternary Deposits, Etc. — Mills. 
ionado and Agua Quente the road passes continuously for about 
a league over a plain paved with a superficial sheet of oxides 
of iron, and Burton speaks of riding over the same plain be- 
tween Agua Quente and Fonseca. ^ It is one of the two plains 
before mentioned. The oxides consist of hematite and limo- 
nite, and are more or less mingled with gravels. They are 
evidently altered bog-ore deposited by waters which obtained 
their iron from the great masses of specular ore (more than 
300 feet thick across the stratification at one place near Catas 
Altas where I measured it) which lie uptilted on the easterly 
flank of Caraca mountain. 
No such sheet of bog-ore could be formed with present 
drainage; for streams flow by the plain from 187 to 320 feet 
lower than its surface, and the streams have rapid currents, 
and there are no bogs or pools of still water of considerable 
size throughout the region. The plain at the highest point 
on the road is about 2,785 feet above sea-level. There can be 
no doubt therefore that the region has been elevated since this 
sheet of oxides of iron was deposited, and that the bog-ore 
was formed when the region was in a low-lying condition, 
with streams flowing nearly at the general elevation of the 
surface, which was the condition as already shown when the 
softened layer of rock on which the sheet of bog-ore now 
rests was formed. 
The other of the two above mentioned plains is much 
smaller than the one just now described, but still a remark- 
able plain for that region. It also is in part at least underlaid 
with iron oxides, and has undoubtedly been preserved from 
erosion by them. The extent of this sheet of oxides is not 
evident because it is overlaid by sandy loess, but it is exposed 
where the road passes down off" the loess. The plain is high 
up near the divide between the waters of the Doce and the 
Gequitinhona, on the slope drained toward the Doce by the Rio 
de Peixe, extending to within about a mile of the divide, at an 
elevation of about 3,416 feet which is somewhat less than 300 
feet lower than that of the divide. The Rio de Peixe falls at 
an average rate of 120 feet to the mile for fifteen miles below 
the plain, and the cascalho and loess fall at nearly the same 
rate ; for at a point 15 miles below, the loess overlies cascalho 
which rests but a few feet below the level of the present stream. 
A bog could not have existed in such a positi on, on a steep 
^^Highlands of Brazil. Vol. i. p. 315. 
