These were very simple in their structure, being composed of whalers' kettles, set in masonry.
These kettles were filled with broken ore about the size of McAdam-stone, mingled with lime.

Another kettle, reversed, formed the lid, and the seam was luted with clay.

On applying heat, the mercury was volatilized and carried into a chimney-stack, where it condensed and flowed back into a reservoir, and then was led in pipes into another kettle outside.

After witnessing this process, we visited the mine itself, which outcropped near the apex of the hill, about a thousand feet above the furnaces.

We found wagons hauling the mineral down the hill and returning empty, and in the mines quite a number of Sonora miners were blasting and driving for the beautiful ore (cinnabar).