Ch. VI.] QUARTZ LODES. 93 



The ore is taken down to the reduction works in 

 waggons that run down by gravitation, and are drawn 

 up again by mules. It is then stamped to powder by 

 iron beaters, each of which is lifted by cams, and let fall 

 seventy times per minute. The stamped ore, in the 

 form of fine sand, is then carried by a stream of water 

 over inclined copper plates covered with mercury, with 

 which is mixed a little metallic sodium. Nearly the 

 whole of the free gold is caught by the mercury, for 

 which it has a great affinitv, and accumulates as 



O / ' 



amalgam on the copper plates, from which it is cleaned 

 off every twelve hours. The sand and water then 

 passes over inclined tables covered with blankets, the 

 fibres of which intercept particles of gold and mercury 

 that have escaped from the first process, and afterwards 

 into a concentrating box, where the coarsest grains of 

 sand and the sulphurets of iron, copper, and silver, are 

 caught, and with the sand from the blankets retreated 

 in arrastres. These arrastres are round troughs, twelve 

 feet in diameter, paved with stones. Four large stones 

 of quartz are dragged round and round in this trough, 

 and grind the coarse sand to fine powder. The gold 

 liberated sinks into the crevices in the stone pave- 

 ment, a little mercury being put into the trough to form 

 it into amalgam. The arrastres and all the amalga- 

 mating apparatus is cleaned up once a month. The 

 amalgam obtained is squeezed through thin dressed 

 skins, and is then of the consistence of stiff putty, and of 

 a silver colour. These balls of amalgam are placed in 

 iron retorts, and the mercury driven off by heat and 

 condensed again in water. These balls of gold so ob- 

 tained are then melted into bars weighing about one 



