1892-93.] NOTES ox THE AMALGAMATION PROCESS. 361 



with the movements of the legs, the legs are raised without bending the 

 knee at an angle from the body, the toes turned out in descending, 

 the heel striking the lamo first, and as the heel touches it the other leg is 

 raised, in this way he proceeds all over his little lamero until it is 

 finished. But notwithstanding all that has been said, there is a loss of 

 the metal contained in the ore as well as the mercury, which is an 

 expensive item ; there is no doubt that during last century, especially 

 towards the end, it (the Patio Process) was at its zenith in Mexico as a 

 metallurgical process, which is borne testimony to by a report about that 

 time by one Jose Acosta, who said that in Potosi alone seven thousand 

 (7,000) quintals of mercury were used annually in dressing the ore, not to 

 mention the mercury recovered from the first washing ; but it has 

 gradually lost ground since until it has been replaced at innumerable 

 mines by other processes. In Mexico the cauldron or cazo process is 

 one that has been used with much success. Without giving a description 

 of it, it might be said that the apparatus instead of being as now a vessel 

 formed either of blocks of stone or wooden staves like those of a tub, the 

 bottom being a slab of copper 2]/^ inches in thickness, the metallic bottom 

 retained the same as the head or bottom of a barrel being retained 

 by a groove running round the interior of the vessel, the original 

 cauldron, as invented by Alonzo Barba, was essentially "to be of copper 

 pure, as any alloy present in the copper would involve the mercury 

 taking it into solution ; they must be in shape inverted cones and flat 

 bottomed, the under part to have a.rim of 6 or 8 inches high and half an 

 inch broad, all beat of one piece ; other plates of copper are fixed in the 

 inside by copper nails, it must be water tight, the inside of the boiler to 

 be lined with lime and ox-blood, the upper part surrounded by iron rings, 

 to which is fixed a crossboard carrying at its centre a spindle with wings, 

 which revolves, agitating the contents of the cauldron." 



The cazo process or hot amalgamation was accidentally discovered by 

 Alonzo Barba. When trying to fix mercury by boiling silver ore, mercury, 

 and water, mixed in a copper dish, he found that he had a shorter method 

 of amalgamation ; he gradually improved, on this and introduced it into 

 practice in Peru, in which it was .successful in its application to the 

 treatment of chlorides, bromides and iodides of silver which are abun- 

 dant in that country, and also the ores containing silver in the free state. 

 It was introduced in the sixteenth century and has been in use ever 

 since. There is no change in the process since it was invented, with the 

 exception of the above mentioned replacement of the cauldron entirely 

 made of copper for the one with merely a copper bottom ; indeed it was 

 averred by Barba that nothing but a cazo of solid copper would do, 

 but the great corrosion of the copper and the consequent expense 



