are composed of granite, four blocks of which revolve in each arrastre, attached to cross-bars of wood. This part of the operation is thought of great importance, for it is upon the perfection of the Molienda, (literally, the grinding,) that the loss of quicksilver is supposed in a great measure to depend. It is performed usually in a covered shed, or "Galera," which, in a large Hacienda like Salgado, from the number of arrastres at work at the same time, is necessarily of considerable extent. From the arrastres the ore is again removed to the Patio, (amalgamation court,) where it is disposed in Tortas, the size of which varies according to the dimensions of the Patio, or the fancy of the Administrador, (overseer.) The number of Montones, (heaps,) contained in each Torta, is consequently uncertain; but the Monton of Guanajuato consists of nine Cargas, and two arrobas, or thirty-two quintals of ore; each carga containing fourteen arrobas of 25 lbs.
The Monton requires three arrobas of salt, (from Colima,) at one dollar, or nine reals the arroba. This is added to the mass three days before any other ingredient.
One arroba of ordinary Magistral, (from Tĕpĕsălār, near Āgŭas Călĭeñtĕs,) or 7lbs. of the very best quality, (Pepena.)
Quicksilver, in the proportion of 3lbs. for every marc of silver that the ores of the Monton are supposed by the amalgamator to contain, and varying,
