The _Tiernan Magnetic Separator consist.s of an endless belt traveling over two drums, within one of which is fixed a series of magnets, which occupy a sector of the drain, so arranged that rather more than one-half of the latter is under magnetic influence. Between the two drums, and immediately below the upper surface of the belt, is another series of magnets, called the stratifying magnets. The ore is fed on the belt from a hopper. which has a device for insuring an equal distribution of the ore across the surface of the belt. The ore is carried forward by the travel of the belt, passes over the stratifying magnets and over the magnets within the drum. As the belt turns over the latter. the non-magnetic material falls off into a bin, while the magnetic particles are retained until the belt passes out of the magnetic field, when they arc dropped into a separate bin.
The Lovell-Finney Magnetic Separator consists of a shaft on which are placed two 30-in. iron disks 50 in. apart. The space between the disks is wound with No. 14 insulated copper wire, forming a solenoid. One end of the shaft is hollow, and through this central aperture are passed the earls of the wire, which connect with the commutator attached to the shaft. From the rim of each disk extend, alternately, a number of iron bars, each bar extending almost to the edge of the opposite disk, but insulated this, as well as from the adjacent bars. The spaces between the bars are filled with non-conducting cement, giving to the finished wheel the shape of a solid cylinder, 30 in. in diameter and .50 in, long. Over this cylinder travels an endless belt of ordinary canvas, held tight by an adjustable pulley. An apron of copper is placed under the magnetic wheel, closely following the curvature of the same. Over the apron the crushed ore is carried by a liberal flow of water. An electric current of 113i amperes and 110 volts is run through the wire of the wheel, winch is revolved at the speed of 14 revolutions per minute. The disks and bars being thus magnetized, the magnetic particles of ore are attracted to the wheel, and attach themselves to the endless belt.
The non-magnetie particles are in the meantime washed off and carried away by the water. When the belt leaves the top of the magnetic wheel it carries with it the collected concen trates, which are shed into a water tank, through which the belt passes before returning to the separator. From this tank the concentrates are lifted by a flight conveyor and deposited directly on the railroad car, ready for shipment. The advantage claimed for this separator is the entire absence of dust, and the wear on the machinery due to the same. According to Mr. Axel Sahlin, a machine at Weldon, N. J., has been in constant operation for nine months, handling about 121 tons of crude ore per day, and the only repairs have been one new canvas belt, costing $5, and one course of new wire cloth for the revolving screen. cost-. ing about $20. The dynamo furnishing the current for this machine required 3 horse-power.
Works ,for Reference.—The Art of Ore-dressing in Europe, by W. B. Kunhardt, 1889 Losses in Gold Anin-lgaination, with .tint's on tlee Concentration of Gold and Silver Ores, by McDermott and Duffield, 1890 ; Mining and Ore-dressing Machinery, by C. J. W. Lock, 1s90 ; ufbei'eitung der Erze, by C. Linkenbach ; of Lauremburg Dressing Works," Berg rand HuelleninannischeZeitung, 1882, xli. 140-144; " Description of Clansthal Dressing Works," ibzal , 1882, xli. 29, et seq. ; The English vs. Continental System of Jig ging," by H. S. Munroe, Trans. Am. Inst. Mining Engrs., xvii. 637 ; " The New Dressing Works of the St. Joseph bead Co.," by H. S. Munroe, ibid,,xvii. 6511 ; " Velocity of Bodies of Different Specific Gravity falling in Water." by R. II. Richards and A. E. 1Voodward, xviii. 6t4; The ..11etallarily of ,Silrer. by Manuel Eissler, 189.
For further details concerning the magnetic concentration of iron ores, see Trans. Am. inst. Mining Engrs., vols. Sviti, and cis.• which contain numerous papers upon the subject.