THE ANCIENT RIVER-DEPOSIT OF THE AMAZON, 763 
59. On the Ancient River-peposit of the Amazon. By C. Bar- 
RINGTON Brown, Esq., F.G.S., Assoc. R.S.M. (Read June 25, 
1879.) 
[Puatre XXXVIII.] 
Ir is my intention to endeavour to describe in this paper the mode 
of occurrence, deposition, and general characters of a vast deposit of 
ancient alluvial matter which forms a 
great portion of the valley of the Ama- 
zon, and to deduce therefrom some facts 
regarding the deposition of detrital 
matters by this great river. 
In ascending the Amazon, one cannot 
fail to be struck by the appearance of 
lines of cliffs at long intervals apart— 
first on one hand, and then upon the 
other—which, rendered conspicuous by 
their bright colouring, form a pleasing 
contrast to the monotonous line of low 
greyish-clay river-sides which elsewhere 
meets the eye. In fact, they on the 
one hand, and a great plain of recent 
alluvium on the other, when the river 
is flowing on one side or the other of its 
present valley, are the chief features in 
the physical geography of the Amazon 
and its tributaries. 
The accompanying diagrammatic sec- 
tion (fig. 1) will explain the relative 
position of the two. 
Exceptions to the above-described 
conditions are only seen on the Lower 
Amazon at Almeyrin and Montealegré 
(where views of some picturesque scenery 
are obtained, produced by sandstone 
mountains of doubtful Triassic age), and 
at Santarem, on the Tapajos river, on 
the Trombettas river, at Parintins, 
Juruty, and Faro (where there are table- 
lands rising, in some instances, to a 
height of 460 feet above the general 
level, which are composed of beds of 
friable sandstone and clay, of grey, 
white, and reddish colours). The age of 
these last-mentioned beds has not been 
determined, owing to the entire absence 5 
of fossil forms; and it is a question whether they belong to the 
upper part of the Triassic sandstone or are of a more recent date, 
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