766 Cc. B. BROWN ON THE ANCIENT 
Coary cliffs are composed of red loam, red clay, and sand, and 
bluish, grey, and reddish clay, in descending order. Here the deposit 
rests upon a bluish arenaceous clay, the surface of which must have 
been much eroded before the deposition of the superincumbent mass. 
The first place where this subjacent stratum is seen is near the mouth 
of the Purus river; and I am inclined to the belief that it belongs to 
the upper part of the Tertiary deposit, sections of which are seen 
further up the Solimées. In this part, however, it does not contain 
any fossil shells, but has a few layers of leaves. 
Not far above Coary are clifis called Tanacoara, where the follow- 
ing section was obtained :— 
ft. 
15 Red loam. 
20 Pink sand beds. 
1 Yellow clay. 
34 Light greenish-grey clay. 
At the upper end of this section the underlying, false-bedded, 
bluish clay makes its appearance, forming further on the full height 
of the river’s bank, with the exception of a few fect of grey clay, into 
which it seems to pass. No portion of it rises above the level of 
high-water mark of floods, which, at the time of my visit, was 40 feet 
above the then level of the water. 
The next Barreira—that of Camara Coary—is composed at its 
eastern end of 70 feet of pinkish and white arenaceous loam, upon 
30 feet of red and yellow sand ; while at its western end we find it 
made up of beds of 
Red argillaceous loam. 
‘Red and white sand. 
Yellowish sand. 
Red sand, resting upon the denuded surface of the blue clay before 
mentioned. 
At Tapera Barreiras, a little further on, this latter assumes a 
rock-like aspect, and its bedding dips eastward at an angle of 5°. 
Motun Coary cliffs differ greatly in their composition, being at 
their eastern end of red loam, resting upon beds of red sand; and at 
their western, of white sand upon white clay. Near their western 
end they are composed of red loam upon yellowish and reddish 
speckled sand, resting upon the subjacent bluish clay, which at this 
spot, where baked by the sun’s rays, has a shale-like appearance. 
Its beds have lines of deposition in various directions and in irregular 
curves. <A thickness of some 10 feet of it was seen above the water, 
which at the time stood at a level of 40 feet below its floodmark. 
It contained some portions of imbedded tree-stems, and its eroded 
surface was covered with a thin layer of hydrated sesquioxide of iron. 
About a quarter of a mile down the river, in the same barreira, 
there was a great and almost circular bay in the face of the cliff, of 
200 yards in diameter, the entrance to which was only about 
50 yards in width. This resembled somewhat the crater of a vol- 
cano, and was an instance of the prodigious power exerted by the 
river in suddenly washing down great portions of its banks. Kn- 
tering the bay in a boat, I had an opportunity of examining its side 
