Arrastra

Early ore-crushing device. Draft animals (oxen, mules, whatever) were hitched to one or more of the cross-pieces, and as they walked in a circle around the middle pivot, the large boulders hanging off the chains would be dragged over the rock-lined patio underneath where the chunks of ore had been dumped. Not very sophisticated, or effective, but it was cheap and could (aside from the chains) be made of local materials. The name comes from Spanish arrastrar, to drag. This is a model at the Jerome mining museum, Arizona.