. Bulletin of the Geological Society of America. Geology. 270 J. C. BRANXER—DECOMPOSITION OF ROCKS IN BRAZIL. Such hills often have a striking resemblance to some of the great glaciated rock surfaces of the north, so round and smooth are they. Indeed, Agassiz was at one time of the o^Dinion that many of those above Rio de Janeiro were roches moiUonnees.'^ In other cases they resemble in outline volcanic cones, f Sometimes there is one abrupt, perpendicular, or even overhanging face, while the other sides slope away at a low angle. The faces of these bare rocks are usually so steep that ordinar
. Bulletin of the Geological Society of America. Geology. 270 J. C. BRANXER—DECOMPOSITION OF ROCKS IN BRAZIL. Such hills often have a striking resemblance to some of the great glaciated rock surfaces of the north, so round and smooth are they. Indeed, Agassiz was at one time of the o^Dinion that many of those above Rio de Janeiro were roches moiUonnees.'^ In other cases they resemble in outline volcanic cones, f Sometimes there is one abrupt, perpendicular, or even overhanging face, while the other sides slope away at a low angle. The faces of these bare rocks are usually so steep that ordinar}^ vegeta- tion can find no foothold on them, although they are usually beautifully adorned with epiphytes, and especially with little gray bromelias, bearing white and pink flowers. Toward the summits on these rocks the lower angles of the faces allow a little soil to accumulate, and here hardy ferns- and such plants as readily withstand drv weather J quickly gain foot- hold, while the summits are often crowned with bushes and even with, large trees. The distribution of these topographic forms corresponds in^ the main with the distribution of the granites and gneisses, and I have never seen them in rocks of an}^ other kinds. It is a noteworthy feature of this exfoliation of peaks that the flakes come to a feather edge on the downhill side, so that they FiGVRv. ^agram iiiusiraiing i/,e E^/oUaiion overlap cach othcr Hkc gigautic- of Cones. ^ . . scales. This is shown in almost every view of these exfoliated mountains. The accompanying diagram exhibits the theoretic arrangement of these crevices on difl'erent slopes. These scales also wrap around the peak, as may be seen in the case of the Gavca (see plate 12). On the shore at Copocabana, on the other hand, these scales seem to be inverted (see plate 11). This, however, may be a local accident. § The most striking illustrations of these forms occur in the Serra do- Mar. They abound in and about Rio de Janeiro, where they g
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