674 GEOLOGY AND MINING INDUSTRY OF LEADVILLE. 



tures provided in the light building, shakes the bags, and the dust with which they 

 are charged falls into the dust-chambers. When a sufficient quantity of this dust has 

 accumulated there, the doors O are opened and a light wood fire is placed through 

 doors d in the fireplace iV^. The soot of the dust soon catches fire, and the dust, which 

 was quite black, like lampblack, becomes white; it becomes also denser by thisoi)era- 

 tion and is more easily manipulated. When the smoke has thus been calcined it is 

 shoveled out through doors 0. 



During a run of five days 3,030 pounds of this calcined dust was caught in the 

 Bartlett filter fi-om one furnace, but the experiment was not altogether satisfactory for 

 the reason that the furnace was worked with an open feed-hole, as with an ordinary 

 dust-chamber, and that the Sturtevaut f;in was drawing as much air as smoke, so that 

 the damper G of tlie furnace had to be left half opcu and about half the smoke was 

 lost. In the conditions in which the experiment was made this could not be avoided, 

 but this is only an experimental defect, impairing in no way the value of the filter, 

 which does its work to perfection; the writer estimates at 7,000 poonds the quantity of 

 dust which would have been caught in five days had the experiment been made with 

 closed feed-hole and damper, or say at 1,500 pouiuls per twenty four hours. The calcined 

 dust has been assayed by Dr. M. W. lies, and found to contain 70 per cent, of lead and 

 6 ounces of silver to the ton ; so that with a furnace of 35 to 40 tons of ore capacity per 

 twenty ibur hours one-half a ton of lead is lost in the air, as well as 4.5 ounces of silver, 

 in twenty-four hours. The result of this is that the quantity of lead lost in the air is 

 greater than the quantity of dust condensed in the dust-chambers. At smelter A, where 

 the dust chamber arrangement is of tlie best kind, 150 tons of dust were collected in 

 182 days, giving 1,048 pounds of dust per twenty-four hours for two furnaces whose 

 joint smelting capacity in tons of ore is equal to that of the furnace connected with 

 the Bartlett Alter. This dust, assaying 35 per cent of lead, represents 577 pounds of 

 lead, or a little over a quarter of a ton. These are indeed important results and are 

 worth considering. 



At smelter B, as at most smelters, chamber-dust is mixed with milk of lime; 

 the mixture is spread over ore-beds and resmelted in this way. The composition of the 

 dust caught in the Bartlett filter is extremely remarkable. It has been analyzed, such 

 as it is ]>revious to calcining, and the results will be found in the study of lead fumes, 

 Analysis XXXVI. 



Smei.tkr C. 



Disposition of works — These works, like all the other smelters situated in Cali- 

 fornia gulcli, are erected on the southern slope of the northern bank of the gulch, tlie 

 gentle slo]ie of this hill favoring singularly the construction of similar establishments. 

 A glance at the vertical section through these works (Fig. 2, Plate XXXI) will siiow 

 their general disposition. A deep cutting, w y z, in the bank is the only one needed 

 for the erection of the furnaces B and dust-chamber D'. In front of the furnaces and 

 extending some little distance is the slag-heap X npon which are seen piles of bullion 

 in bars. A, ready for shipment. At the fooi of the slag heaps runs the lower road of 

 California gulch. The furnace JS is connected by means of the sheet-iron flue/ with 

 the dust-chamber D'. The water jackets of the furnace are sujiplied with water from 

 the main water-pipe «i, connected with the tank 1>, placed on the feeding-floor YZ, and 

 constantly filled with water by means of pumps worked by machinery. The sheet iron 



