52 MEXICAN RESOURCES. 



mud, and the last one to effect the discharging. Inside those vats is a four-arm 

 churn-staff, which by its revolutions dissolves the mud, allowing the latter to 

 remain at the surface of the water all the time necessary for the sflver and 

 quicksilver to settle themselves at the bottom. Before commencing to wash the 

 cake, it must be softened by water in as large a quantity as to have the mud 

 thoroughly fluid. Then the mud is carried through a large channel made on the 

 very floor of the arrastre, dragging it along by means of a frame of laths pulled 

 by a mule, until the mud is thrown into the first vat, called cargadora. When the 

 filling operation is over, with the vats half-full with water, the churn is caused to 

 rapidly revolve during half an hour, — an operation called batir (to beat) ; then the 

 vats are filled up with water, the churn is slowly revolved (asentar, to settle) during 

 an hour and a half, at least, in order to be sure of the operation ; then the dis- 

 charging follows. But a trial is made before, to see whether the settling has been 

 perfectly made, introducing into the last vat but one a small vessel hermetically 

 closed, which, when level with the vat-hole, is opened by means of a peculiar device, 

 its contents being received into a gourd, there to be assayed. If the settling has 

 been perfect, a stripe of quicksilver lis or offal appears, which on being rubbed 

 does not form any globule, also some pyrites and terreous parts ; but, should the 

 stripe give forth any quicksilver globule, then the settling has been imperfect, and 

 must be continued until the above-mentioned characteristics are obtained. Then 

 the discharging begins, unstopping the last vat, called piojo, in order to have it 

 emptied down to the opening level. Another assay is made, for security's sake, 

 so that any defect noticed may be corrected at once. 



The vats are filled up again, repeating all the aforesaid operations, until the 

 whole of the cake is washed. Then comes the rinsing operation (en jiiagar), 

 pouring fresh water into the vats, beating and settling again, so as to clean out 

 all the mud. 



As the quantity of mud put in each filling is proportional to the capacity of the 

 vats, the washing takes more or less time. Vats 3™ 35 diameter by im 67 deep, 

 generally contain three or four montones. As each partial washing takes about two 

 hours, to wash a cake of one hundred montones requires three or four days. When 

 the respective situations of the yard and the washing-place do not allow the mud 

 to be dragged as aforesaid, it is carried by men in large troughs. 



Apitrar (to purify). — This is the next operation, consisting in taking from the 

 vats the settled metal, the larger part of which is found in the first vat, mixed up 

 with cabecilla, that is to say, the ore, which, not being reduced to mud, appears 

 like sand. This sand is put into large and deep troughs, which are kept over the 

 water in a large basin, and undergo an oscillatory and revolving movement, so 

 that the metal may settle at the bottom, adding to that end a quantity of quick- 

 silver, which leads down the smaller particles. 



As the metal so gotten contains, however, earth and other impurities, the cleans- 

 ing operation {limpia) comes next, to have the metal completely purified. The 

 mass of crude metal is taken to the azogueria, where it is thrown into a circular 

 stone basin well covered with bitumen : more quicksilver is added to it, stirring 

 it through, so that the impurities remain at the surface. If some hard grains be 

 found, they are taken out and ground, incorporating them afterwards with the mass 

 in the basin. 



When the mass of crude metal is thoroughly cleaned, it must be dried, so as to 



