Polytechnic Association Proceedings. 933 



crushing the ore by attrition; this is by rubbing the one piece of 

 the stone with the other. I have seen four hundred pounds of 

 hard quartzose Mexican silver ore pulverized in eighteen minutes' 

 time to a powder so fine that most could pass through a No. 100 

 sieve. It weighs about four tons, and is very simple and compact 

 in its construction. 



The old amalgamating system of running the pulverized ore 

 with water over amalgamated copper plates is now gradually giving 

 way to more perfect, though more complicated methods. Some 

 run the ore into variously constructed pans, where, with assistance 

 of heated water, a more perfect mechanical mixture of the ore with 

 the mercury is obtained. This is more especially the case since 

 Professor Henry Wurts, of this city, has made the interesting 

 discovery that the addition of a small portion of sodium metal to 

 the mercury increases the aflSnity of the gold for the amalgam; in 

 most cases a considerably increased yield of gold has thereby been 

 obtained. The Freyburgh barrel, as well as Wykofi's process of 

 boiling the ore with salt water and mercury, whereby some of the 

 sulphurets are decomposed, have, when carefully worked, given 

 good results. Another, the " Staats amalgamator," treats the pul- 

 verized ore in a closed and heated revolving iron boiler, with steam 

 and mercurj^ (in vapor form), whereby also very favorable results 

 are obtained. I beg to mention here my own recently-invented 

 gold extractor, whereby in twenty-four hours ten tons of tailings 

 or pulverized ore can be worked by one man at a cost not exceeding 

 fifty cents per ton. One of these machines (engine and boiler, six- 

 horse power, not included) can be made for one thousand dollars. 

 The cost of amalgamating by the most ordinary method is about 

 one dollar per ton. 



My g^ld extractor has one great advantage over others, and this 

 is that no handling of plates nor separate distillation is required, 

 the same all being done automatically. The retort is connected 

 with the mercury-bath in such way that the amalgam can be run 

 into the retort and the gold obtained without disturbing the opera- 

 tion by distillation in vacuum. A very efficient chemical agent 

 assists in decomposing the sulphurets. 



We will now take up another system of treating the gold ores — 

 the chemical method. "We will subdivide it into the wet and dry, 

 or fire treatment. The wet method we will call that by which the 

 gold is extracted from the ore in the form of an aqueous solution, 

 the so-called chlorine process. As. however, this treatment requires 



