TRANSACTIONS OF THE SECTIONS. 25 



edge with the" greatest ease, and thrust them out one after the other, as one might 

 thrust out a knot of wood from the edge of a board. The prisms reminded him of 

 the construction of a stone wall built without mortar in a slaty country. To com- 

 plete the resemblance, the irregular stones Should form a compact mass, and the 

 surface of the wall should be ground smooth. This ice he always found to 

 resist the eifect of heat more successfully than ordinary ice. He observed that 

 the axes of aU the prisms, in the vertical colmnns of which he had spoken, lay 

 horizontally. 



On a New Method of extracting Gold from Auriferous Ores, 

 By F. Crace-Calvert, F.E.S., F.C.S. 

 At the present time, when the auriferous ores of Great Britain are attracting 

 public attention, it may be advantageous to persons interested in gold-mining to 

 Be made acquainted with a new and simple method of extracting gold from such 

 ores, which presents the advantages of not only dispensing with the costly use of 

 mercm-y, but of also extracting the silver and copper which the ore may "contain. 

 Further, it may be stated that the process can be profitably adopted in cases where 

 the amount of gold is small, and the expense of mercury consequently too great. 

 I need not enter here into all the details of the nimierous (about one hundred) 

 experiments which I made some years since, before I finally arrived at the new 

 method of extracting gold, which I have now the honour of communicating. I there- 

 fore propose the following plan for extracting the gold on a commercial scale : — The 

 finely reduced aiu'iferous quartz should be intimately mixed with about one per 

 cent, of peroxide of manganese ; and if common salt be used, this material should 

 be added at the same time as the manganese, in the proportion of three parts of salt 

 to two of manganese. The whole should be then introduced into closed vats, 

 having false bottoms, upon which is laid a quantity of small branches covered with 

 straw, so as to prevent the reduced quartz from filling the holes in the false bottom. 

 Muriatic acid should then he added if manganese alone is used, and diluted sul- 

 phuric acid if manganese and salt have been employed, and, after having left the 

 whole in contact for twelve hom-s, water should be added so as to fill up the whole 

 space between the false and true bottoms with fluid, This fluid should then be pumped 

 up and allowed to percolate through the mass, and after this has been done several 

 times, the fluid should be run oil into separate vats for extracting the gold and 

 copper that it may contain. To effect this, old iron is placed in it to precipitate 

 the copper ; and after this has been removed, the liquor is heated to drive away 

 the excess of free chloiine, and a concentrated solution of sulphate of protoxide of 

 iron, or green copperas, must be added, which, acting on the gold-solution, wiU 

 precipitate the gold in a metallic form. By this method both gold and copper are 

 obtained in a marketable condition. If silver is present in the ore, a slight modifi- 

 cation in the process will enable the operator to obtain this metal also. It is simply 

 necessaiy to generate the chlorine of the vitriol, manganese, and chloride of sodium 

 process, taking care to use an excess of salt, tliat is, six parts instead of three, as 

 above directed. The purpose of this chloride of sodium being to hold in solution 

 any chloride of silver that may have been formed by the action of chlorine on the 

 silver ore, and to extract the metal, the following alteration in the mode of precipi- 

 tation is necessaiy : — Blades of copper must be placed in the metallic solutions, to 

 throw down the silver in a metallic form, then blades of iron to throw down the 

 copper, the gold being then extracted as previously directed. I think the advan- 

 tages of this process are, 1st, cheapness; 2nd, absence of injury to the health of the 

 persons employed ; 3rd, that not only is the metallic gold in the ore extracted (ai? 

 IS done by mercury), but it attacks and dissolves all gold which may be present in 

 a combined state, besides enabling the miner also to extract what silver and copper 

 the ore may contain. I cannot, however, conclude without reminding you of what 

 is generally underrated — that is, the heavy expenses which attend the bringing of 

 the ore to the surface of the gi-ound, and crushing and preparing it for being acted 

 upon either by mercury or by any other agents. 



