C. F. Hartt— Geological Survey of Brazil. 469 



mend liim for the firmness with which he struggled against 

 great difficulties and for the good results that he obtained. As 

 the rocks of the cachoeira [rapids] are excessively black and the 

 water is white, it was very difficult to photograph both at the 

 same time. On this account I thought it better to make several 

 separate photographic studies of parts of the cachoeira which could 

 be mounted as one picture. I hope that I shall be able, by means 

 of the geological, topographical and photographic material col- 

 lected, to present clear and exact ideas of this wonder of Brazil. 

 From this place a trip was made to the Serra* de Maria Far- 

 inha, distant about five leguas.f From the summit of this ridge, 

 at an altitude of two thousand feet or more, may be seen a very 

 large portion of the provinces of Sergipe and AlagoaS; with parts 

 of the provinces of Bahia and Pernambuco, and thus a very ac- 

 curate idea of the topography of the included area may be ob- 

 tained. All this portion of the country is composed of gneiss 

 and related rocks, foiTning a plateau less than one thousand feet 

 in height, and nearly level or with very slight undulations. As 

 the region is arid, there has been scarcely any decomposition of 

 the rocks, and the effects of water action are not very evident, 

 owing to the absence of rain during the greater part of the year. 

 There is no vegetable mould, but the rock is covered with a 

 layer of sand a few inches in depth. The vegetation is such as 

 is peculiar to arid plains — gigantic cactuses, the aique-xique, 

 faxeiro, mandacaru, etc., being abundant. The rivers run in shal- 

 low channels, and are completely dry during a great part of the 

 year, as are also the small lagoons which abound on the plain just 

 as upon its continuation in the interior of Bahiji. 



From point to point peaks or short serras rise abruptly from 

 the plain, like islands in the sea, seldom attaining an altitude 

 greater than twenty-five hundred feet. In the provinces of Ser- 

 gipe and Alagoas the serras are commonly composed of gneiss 

 or some other rock of the same series. Between Piranhas and 

 the rapids, however, small ridges of sandstone are encountered, 

 and in the provinces of Bahia and Pernambuco, in the neigi)bor- 

 hood of the Sao Francisco River, there are large serras and high 

 ckapadas [table lands] composed of the same rock. Such are 

 the serras of Tacaratii. Long ago this sandstone covered the 

 whole of this region ; but by the action of the sea during the 

 elevation of the Brazilian Plateau, and afterward by the action 

 of the pluvial waters, these beds were denuded over a large por- 

 tion of the country, leaving only the isolated fragments now 

 forming the table-topped hills which abound in the valley of the 

 * The term serra, as used in Brazil, signifies a rocky ridge, usually more or less 

 serrated in outline, although even table-topped hills are often thus designated.— 

 t The Portuguese legua, or league, is equivalent to nearly 1-6 EngUsh miles.— 



