1S79.J ^°° [Derby. 



and sandstone of the second region, and above this a bed, 100 metres or 

 more in thickness, of amygdaloidal and porphyritic trap, apparently a kind 

 of trachyte. The amygdaloid is full of beautiful agates. This second 

 escarpment is the beginning of the third geological region, the topographi- 

 cal features of which are very similar to those of the second or Campos 

 Geraes region, — that is, produced by denudation on horizontal beds. The 

 escarpment extends entirety across the province, in a north-south direction, 

 and into the province of Sao Paulo, where I have recognized the same 

 rock, in the margin of the plateau, west of the Piracicaba river. South of 

 the river Iguassu, I am informed by Mr. Luis Cleve, a very competent ob- 

 server, that it bends eastward, under the name of Serra de Espigao, and 

 extends as far as the Serra do Mar. Prof. Hartt had already observed that 

 the Serra do Mar, in Santa Catharina, is capped by phorphyritic trap. It 

 is probable, therefore, that these rocks cover the greater part of the in- 

 terior of that province, as well as the neighboring portion of Rio Grande 

 do Sul, in which agatiferous trap is common. A portion of the Republic of 

 Uruguay probably belongs to the same formation. To the west the coun- 

 try is unexplored, but from the scanty information I could obtain, it seems 

 probable that the trap formation extends to the river Parana. 



The surface of this region is, in general, a heavily wooded plain, but 

 has several extensive campos, the most important ones being those of 

 Guarapuava, which unite, to the south, with the extensive campos of Rio 

 Grande do Sul. There appears to be a slight inclination towards the 

 Parana, and the river valleys being deep, present high steep slopes, that 

 have been dignified by geographers, as well as the common people, as 

 mountains. In point of fact, no true mountains exist in the province, out- 

 side of the metamorphic area. 



No very definite data exists for determining the geological age of this 

 enormous outflow of trap. It is certainly later than the Devonian, and is 

 most probably Mesozoic. In lithological characters both the trap and the 

 red sandstone, which appears to be associated with it, and to be distinct 

 from the underlying Devonian series, resemble in a striking manner the 

 Triassic rocks of eastern North America. 



The drainage of the province is determined by the above described topo- 

 graphical features, and is principally toward the Parana, only one large 

 river, the Ribeira, flowing directly to the Atlantic. This river rises north 

 ofCurityba, in the mountainous Assunguy region, and flows northward, 

 into the province of Sao Paulo, breaking through the Serra do Mar, above 

 the city of Iguape. Some of its tributaries flow down the slope of the 

 Serrinha, and have cut ravines, indenting the margin of the sandstone 

 region, but can hardly be said to drain any part of the Campos Geraes. 

 In the same metamorphic region, between the Serra do Mar and the 

 Serrinha, rises the principal river of the province, the Iguassu, which flows 

 first southward and then westward, traversing the second and third re- 

 gions, to empty into the Parana. Passing over several almost unknown 

 rivers, belonging exclusively to the third region, we come to the Ivahy, 



