Note (return) — Chapter XII · VOYAGE ROUND THE WORLD, BY CAPTAIN GEORGE SHELVOCKE, IN 1719-1722.

It may naturally be supposed that mines, as well as other things, are subject to variation in their productiveness. The mines which, till very lately, yielded most silver, were those of Oroura, a small town about eight leagues from Arica. In the year 1712, one was discovered at Ollachea near Cusco, so rich that it yielded 2500 marks of silver of eight ounces each, or 20,000 ounces, out of each caxon or chest, being almost a fifth part of the ore; but it has since declined much, and is now [1720] only reckoned among the ordinary sort. Those of Lipes have had a similar fate. Those at Potosi now yield but little, and are worked at a very heavy expence, owing to their excessive depth. Although the mines here are far diminished in their productiveness, yet the quantity of ore which has been formerly wrought, and has lain many years on the surface, is now thought capable of yielding a second crop; and when I was at Lima, they were actually turning it up, and milling it over again with great success. This is a proof that these minerals generate in the earth like all other inanimate things;3 and it likewise appears, from all the accounts of the Spaniards, that gold, silver, and other metals are continually growing and forming in the earth. This opinion is verified by experience in the mountain of Potosi, where several mines had fallen in, burying the workmen and their tools; and these being again opened up after some years, many boxes and pieces of wood were discovered, having veins of silver actually running through them.4