484 



METALLURGY. 



tions. It is a bronze, with the addition of 

 lead and antimony, and is composed of copper, 

 15 parts; tin, 2-34 parts; lead, 1-82 part; and 

 antimony 1 part. 



Great hardness and ductility are given to 

 red brass by mixing in with the metals a small 

 quantity of green bottle-glass. While the re- 

 sultant alloy is not easily worked, it is valua- 

 ble as a mixture in making other qualities of 

 brass, for which purpose borings, filings, etc., 

 can be used with advantage. It is adapted 

 for use in machinery by melting with it one 

 per cent, of oxide of manganese. All sorts of 

 brass made with this alloy are very liquid and 

 close grained. 



On account of their power of resisting the 

 corrosion of sulphurous mine- waters, signal 

 ropes made of Delta wire have been found to 

 be much better for use in mines, collieries, etc., 

 than those made of iron. Messrs. Grille, of 

 Dusseldorf, find them to possess just double 

 the tensile strength of the galvanized-iron wire 

 formerly used by them. This allows the weight 

 of the wire to be reduced one half. 



A prize of $750 was offered by the Berlin 

 Union for the Promotion of Industrial Activity 

 for the most exhaustive critical summary of 

 the bronze, red brass, and brass alloys, used 

 or recommended for use in mechanical science. 

 Papers for the competition were required to 

 be sent in by Dec. 31, 1887. 



Gold, The treatment of gold-ores in the ar- 

 rastra is of interest, because the principle of 

 the apparatus is copied in the new methods 

 that are being devised. The machine is slow, 

 but effective. As used in Mexico, it is built 

 with a circular pavement from six to ten feet 

 in diameter, of the hardest and toughest rock 

 that can be found, which should also be coarse 

 grained and have a rough surface; but all 

 joints should be tightly cemented to prevent 

 waste of gold. In the center of the pavement 

 is fixed a pivoted post, which carries a little 

 above the floor-level two or more arms, to 

 which stone drags are hung, lifted up a little 

 in front, but scraping the ground behind, and 

 weighing from 80 to 300 pounds or more. This 

 machine is moved by such power as is most 

 available. The outside of the pavement is 

 protected by a tight wall, from 18 to 30 inches 

 high. The ore to be treated in the arrastra is 

 broken to the proper size, shoveled or fed in, 

 and mixed with water enough to make a thick 

 pulp. A charge consists generally of from 

 600 to 1,000 pounds of dry ore. The drags are 

 allowed to act from two to four hours, the 

 limit of time being fixed by testing the fineness 

 of the pulp between the thumb and finger. 

 The principal chemicals used with gold-ore are 

 a little potassium cyanide to " liven " the 

 " quick," or some wood-ashes or lye to neutral- 

 ize the effect of any grease that may have got 

 into the ore. Generally, no others are em- 

 ployed; but when the ores carry large amounts 

 of silver, copper sulphate (Milestone) and salt 

 are put in solid, in such quantities as seem ne- 



cessary. When the pulp has been ground long 

 enough, the mercury is added, in quantities 

 depending on the precious-metal contents of 

 the ore. The time required for the operation 

 is from six to ten hours. The capacity of the 

 simplest arrastra varies with the kind of treat- 

 ment, and the completeness of the plant, from 

 one to two tons a day. The amount of labor 

 required in this process is extremely small. 



" Black gold" has been found by Mr. K. W. 

 E. Mclvor's analysis of a specimen from the 

 nuggety reef at Maiden, Victoria, to be ana-, 

 tural alloy of gold and Bismuth. The ore is 

 crystalline, malleable, of silvery-white luster, 

 when freshly broken, but tarnishing and be- 

 coming black on exposure. When roasted, the 

 bismuth is eliminated, and a bead of pure gold 

 is left. The ore contains gold, 64-211 ; bismuth, 

 34-378; and siliceous matter, 1-391. 



The essential conditions of a successful amal- 

 gamation process with gold are to maintain tho 

 mercury in a condition of " quickness," so that 

 it may readily take up every atom of gold pre- 

 sented to it, and to keep the pulverized ore 

 in contact with the clean mercury. These con- 

 ditions are insured in Mr. B. 0. Molloy's hy- 

 drogen-amalgam process. In this process the 

 mercury is placed, to the thickness of about 

 inch, in a pan, in the center of which is a por- 

 ous jar having within it a cylinder of lead and 

 a solution of sulphate of soda. The lead cyl- 

 inder is connected with the positive, and the 

 mercury with the negative pole of a small 

 dynamo. When the current passes, oxygen is 

 evolved from the surface of the lead anode, 

 while hydrogen is evolved from the surface of 

 the mercury. The mercury combines with a 

 portion of the hydrogen, and so forms a hydro- 

 gen-amalgam, while the excess of hydrogen 

 passes away. The mercury thus charged with 

 hydrogen can not oxidize, and, no matter how 

 deleterious the ingredients of the ore may be, 

 it is always quick, and its affinity for the gold 

 is manifested by a perfect amalgamation. 



Gold has been discovered near Ishpeming, 

 Mich., on the Lake Superior Iron Company's 

 workings. A fairly rich seam of auriferous 

 quartzite lies at a depth of about four feet from 

 the surface; while from twenty feet depth 

 specimens were obtained which would give an 

 average run of $10,000 to the ton in native 

 gold. The gold is said to be so thick that it 

 holds a mass of quartz together after it has 

 been broken with the hammer. The gold- 

 bearing belt seems to extend in a fairly defined 

 line from Marquette to L'Anse, some 60 miles, 

 and is from 2 to 8 miles north of the iron-belt. 



Herr M. Dahl, mining engineer, who has 

 been examining northern Norway, on behalf 

 of the Norwegian Government, reports that 

 all the rivers in the interior of Fiunmarken, a 

 district of fifty Norwegian square miles, carry 

 gold. The metal is found in sand contained 

 in little hollows, which by their shape prevent 

 its being washed away by the water. Platinum 

 is also found occasionally. 



