118 Geology of South America. 



west 38° south. This system, which M. D'Orbigny names the 

 Brazilian system^ would seem to be one of the most ancient 

 which we can trace through the posterior modifications of the 

 crust of the globe. M. Pissis regards it as anterior to the 

 transition formations of Brazil, and perhaps it preceded the 

 soulevement of the most ancient system of mountains hitherto 

 described in Europe. It is probable that it affects to great 

 distances the fundamental rocks of America ; for the general 

 direction which we have just indicated differs but little from 

 that of N. 45° E., which M. de Humboldt, at the beginning of 

 this century, pointed out in the slaty rocks of the coast of 

 Venezuela, and in the mountains of granitic gneiss, from the 

 lower Orinoco to the basin of the Rio-Negro and of the Ama- 

 zon.* 



Nevertheless, the hills of gneiss which occur in the Pampas 

 between Cape Corientes and the Sierra of Tapalquen, as well 

 as the hills of Monte Video, are characterised by a different 

 direction, running from W. 25° to 30° N., to E. 25° to 30° S. 

 M. D'Orbigny gives them the provisional name of Pampean 

 system, and he thinks that this system is nearly as ancient as 

 the Brazilian system. If subsequent observations confirm this 

 conjecture, the relations of these two systems, whose direc- 

 tions are nearly perpendicular to each other, will naturally 

 recal the relations which subsist in Europe between the West- 

 moreland system and the system of the Ballons. 



In the midst of the multitude of dislocations of which the 

 Silurian series presents traces, M. D'Orbigny has endeavoured 

 to ascertain the soulevements which affected this system before 

 it was covered by subsequent formations, but he has not been 

 able to define any one of them with certainty. He has not 

 succeeded better with the Devonian system, for a most atten- 

 tive examinat'.on of the innumerable multitude of mountains 

 and hills belonging to this series has not enabled him to dis- 

 cover any system of dislocations specially limited to itself; but 

 in Brazil M. Pissis has pointed out a system of dislocation 

 which he regards as immediately posterior to the formation 



* Humboldt's Essai Geognostique sur le Gisement des roches dans 

 les deux hemispheres, p. 5Q, 



