The ores which I have the honour to submit for your inspection were collected by me in Chili. They consist of numerous compounds of copper, silver, gold, &c., and represent the very varied minerals obtained in that country.

Besides the primary metal there is usually at least one secondary body of value present.

The proportion in which this secondary metal—I mean secondary as regards quantity—is present in metallic ores does not seem to be a mere chance affair, but seems to follow some law. My attention was directed to this matter by the silver ores from the district of “Lomas Bayas” near Copiapó. These ores contain gold in a certain proportion, not in relation to the gross weight of the ore but to the contents in silver.