278 J. C. BRANNER — DECOMPOSITION OF ROCKS IN BRAZIL. 



Angra dos Reis, in the southern part of the state of Rio de Janeiro * 

 Mr Darwin speaks of havino- seen at Rio "large sized boulders of green- 

 stone." f 



In the region northeast of Rio the}" are locally abundant from the bay 

 to Bahia, varying in size from a few inches to more than fifty feet in 

 diameter (see plate 14). They are more abundant in the mountainous 

 and hill}^ regions, but they are not confined to them. J Some enormous 

 blocks, 25 or 30 feet in diameter, have been cut through in building the 

 highway and railway from the foot of the Serra to Petropolis.§ Here 

 and there they have been left perched upon points and ledges by the 

 decay and removal of the rock from about them.|| 



Many striking illustrations occur at and about Itatiaia, in western Rio 

 de Janeiro. A beautiful example is figured b}'' Homem de Mello at this 

 peak.^ Along the line of the Pedro Segundo railway they may be seen 

 all the way from Rio de Janeiro to near Barbacena. In the interior of 

 Minas similar boulders are found wherever the granites, gneisses or other 

 crystalline rocks occur.^* The^y are abundant along the valley of the 

 Parahybuna, both in Minas and Rio de Janeiro ; on the Serra das Abo- 

 boras near Parah3"ba do Sul ; ft on. the southeast spur of the Serra de S. 

 Geraldo near Uba, in southeastern Minas ; XX oi^ the summit of the ridge 

 north of S. Joao Baptistanear 01iveira,§§ and also between Trigueira and 

 Bom Dispacho.llll In Goyaz there are enormous blocks of gneiss between 

 Ciganos and Estalagem, in the valley of Rio Santa Thereza, ^^ Central 

 Goyaz. 



In the state of Parana, at the port of Paranagua, the telegraph-signal 

 hill above the village of Cutinga is of granite and has many large boul- 

 ders of decomposition on and about it. They flank the Morro da Penha 

 at Victoria.^^'^-^ There are great numbers of granite boulders at the fiills of 

 the Jiquitinhonha, on the border line between Bahia and ]\[inas,ttt ^i^d 



*Beiti"age zur Gebirgskunde Brasilieus, p. 31. 

 t Trans. Geol. Soc, 2d ser., vol. vi, 1842, p. 427. 



I Reise nach Brasilien. H. Burmeister. Pp. 184, 185, 212, 213. Agas.siz: Journey in Brazil, pp. 

 101,486,488,491,493. Reise in Brasilien. Spix u. Martins, Mi'inchen, 1825, i, p. 1G6. Travels in 

 Brazil, i, p. 249. 



g A photograph of one of these blocks is reproduced in Dent's "A Year in Brazil," p. 424, 



II Keller-Leuzinger\s Amazon and Madeira Rivers, p. 48 ; Burton's Highlands of Brazil, vol. i, p. 64. 

 1[ Excursoes geographicas. Revist. de Inst. Hist, do Brazil, li,pt. 2, pp. 167, 178; xxix, pt. i, pp. 



41.3-418. 



**See also Helmreichen's Geognostisehe Vorkommen der Diamanten, pp. 5, 7, 12, 16. 



ft Gardner's Travels in Brazil, p. 521. 



JtBeitriige zur Gebirgskunde Brasiliens. W. L. von Eschwege. Berlin, 1832, p. 186. 



g§ Beitn'ige zur Gebirgskunde Brasiliens. Joh. Em. Pohi. Wien, 1832, p. 26. 



Illj Expedition dans les parties centrales de l'Am6rique du Sud. Francis de Castelnau. Paris, 

 1850, i, pp. 376, 378, 311. 



^f Op. cit., ii, pp. 84-86. 



*** Geology and Physical Geography of Brazil, p. 70. 



ttt Travels in Brazil. Prince Maximilian. London, 1820, pp. 302, 304, 306. 



