In the great yard, numbers of men and horses were walking round and round upon the “tortas,” tarts or pies, as they are called, consisting of powdered ore mixed with water, so as to form a circular bed of mud a foot deep. To this mud, sulphate of copper, salt, and quicksilver are added, and the men and mules walk round and round in it, mixing it thoroughly together, a process which is kept up, with occasional intervals of rest, for nearly two months. By that time the whole of the silver has formed an amalgam with the mercury, and this amalgam is afterwards separated from the earth by being trampled under water in troughs. We were surprised to find that men and horses could pass their lives in wading through mud containing mercury in a state of fine division without absorbing it into their bodies, but neither men nor horses suffer from it. We happened to visit the melting-house one evening, while silver and lead were being separated by oxidizing the lead in a reverberatory furnace. Here we noticed a curious effect. The melted litharge ran from the mouth of the furnace upon a floor of damp sand, and spread over it in a sheet. Presently, as the heat of the mass vaporized the water in the sand below, the sheet of litharge, still slightly fluid, began to heave and swell, and a number of small cones rose from its surface. Some of these cones reached the height of four inches, and then burst at the top, sending out a shower of red-hot fragments. I removed one of these cones when the litharge was cool. It had a regidar funnel-shaped crater, like that which Vesuvius had until three or four years ago. The analogy is complete between these little cones and those on the lava-field at the foot of the volcano of Jorullo, the celebrated “hornitos;” the concentric structure of which, as described by Burkart, proves that they were formed in precisely the same manner. Until lately, the formation of the great cone of Jorullo was attributed to the same kind of action as the hornitos, but later travellers have established the fact that this is incorrect. One of the De Saussure family, who was in Mexico a few years back, describes Jorullo as consisting of three terraces of basaltic lava, which have flowed one above another from a central orifice, the whole being surmounted by a cone of lapilli thrown up from the same opening, from which also later streams of lava have issued.