Arizona republican., 1902-12-29

and the hoisting engine Is of such a type that the descending car assists in the work of hoisting the loaded one. As the incline is about 20 per cent to the horizontal the hoistlng operation can be pushed to the limit of speed without danger of jumping the track.
 Electricity is used throughout for lighting purposes in the shafts ana tunnels when necessary, and machine drills are in operation everywhere where the nature of the ground ana vein will permit. These machine drills are operated by compressed air., the power being developed on the surface and conducted down the shafts to dis tributing stations below il pipes, from which places thick walled rubber hos, leads to the different machines. Com pressed air is also used to operate some underground hoists in number or winzes. The skips are for the mos, part self-dumping devices which empty Into bins at the top of the shaft. ana require no extra labor other than that of the engineer at the hoist. The min, contains some twenty miles of track. including the shafts. drifts. etc.
 The method of working the mines IS simple and economical. The shaft fol- lows on the dip of the vein. At every 70 level drift is run lengthwise of the vein at right angles to and on both sides of the shaft. The waste in tae drift is shot down first and hoisted or conveyed to other places to be used as filling; then the ore is shot out anc hofstcd to the bins. This gives a series of parallel drifts in the ore body. one below the other. From a drift the orc IS Sto9ed out upwards to the drift above. The ore is worked out from tn, sides of this chute. the stope timbered cribbed and back-filled with waste as fast as the work proceeds, while the ore is thrown into the chut@aud caught in cars in the drift below. This method proceeds from one drift to another un- til the entire vein is stoped out and cribbed and back filled. leaving only the drifts and chutes open for passage ways of ore and air. One of the stopes thus worked is 1 900 feet in length. Lit tie square set timbering is necessary, as the vein varies from six inches to nine feet In width, and so a nine-foot room is as high as is ever necessary Nearly all the timbcring in the stopes is done with stulls, which do very well as the room is net open long. being cribbed and backfilled with waste as soon as the ore is removed.
 Good natural ventilation is obtained throughout the mine, being obtained by using one shaft as a down drift and another as an up-shoot. regulating tn, circulation in the drifts by means nr doors. Of course some of the stopes in the lower levels are very warm. ana the miners work trin hut he ,;- pure and for the most part moderately cool.
 A small percentage of the ore is fre, milling quartz. but the larger portion of it is sulphides in a quartz matr:x. The country rock in the lower portions of the mine is granite. and exceedingly, hard. Although the shafts and work ings in some instances are exceedingly deep. the mine is exceptionally dry. anG no pumping is necessary to keep tn. passages free from water. All the water used in the works is obtained from supply nine miles from the camp. and Is conveyed over the hills in a for-- Inch pipe, using two pumping stations
 The ore is carried from the bins at the hoists in hand push cars to the stamp mills. In the year 1900 another i"0'0Ahp ihAiI NcS Duhl, SlNlnB q pat tery of eighty stamps now in commis- sion. The ore is conveyed to the mills. dumped into the grizzlies and from there the sized ore passes into the feed bins below. The ore that will not pass the grizzlies passes over into a stall. from which 1t is fed into rock crushet anc then drops into the same feed bins as above. The crushed ore is then dis tributed by gravity into separate bins. which supply each battery of five stamps. The ore is fed into the stamps oy an automatic feed attachment worked by d shoulder which is fastene I 10 the middle stamp shaft of each battery. This shoulder strikes a lever every time the stamp descends, anc the lever opens feed gate for an in stant and allows the ore to drop down.
 The stamps have crop of six inches and strike about ninety times per minute, using a medium weight stamp. Fine crushing is necessary, as the quantity of pyrites in the ore is excessive. in which the ore is very in timately mixed, and so the tonnage per stamp per day is rather low compared with that of free milling ores. The stamps drop in order 1. 4 2. ,, 3. No attempt at refining is made at the min so the product of the mortar boxes is piped direct to the concentration ta- bles, of which there is one for each battery of five stamps In the old miu