How Can We Infer The Absolute Sterility Of The Primitive Rocks Of Guiana From Testimony Merely Negative, From The Circumstance That During A Journey Of Three Months We Saw No Auriferous Vein Appearing Above The Soil?

In order to bring together whatever may enlighten the government of this country on a subject so long disputed, I will enter upon a few more geological considerations.

The mountains of Brazil, notwithstanding the numerous traces of embedded ore which they display between Saint Paul and Villa Rica, have furnished only stream-works of gold. More than six-sevenths of the seventy-eight thousand marks (52,000 pounds) of this metal, with which at the beginning of the 19th century America annually supplied the commerce of Europe, have come, not from the lofty Cordilleras of the Andes, but from the alluvial lands on the east and west of the Cordilleras. These lands are raised but little above the level of the sea, like those of Sonora in Mexico, and of Choco and Barbacoas in New Granada; or they stretch along in table-lands, as in the interior of Brazil.* (* The height of Villa Rica is six hundred and thirty toises; but the great table-land of the Capitania de Minas Geraes is only three hundred toises in height. See the profile which Colonel d'Eschwege has published at Weimar, with an indication of the rocks, in imitation of my profile of the Mexican table-land.) Is it not probable that some other depositions of auriferous earth extend toward the northern hemisphere, as far as the banks of the Upper Orinoco and the Rio Negro, two rivers which form but one basin with that of the Amazon?

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