FUELS AND FLUXES USED IN SMELTING. 643 



Both doors being left open to create a draft, a charcoal and dry-wood fire is kindled 

 at tne door A. Both doors are then closed and hermetically sealed with clay, and the 

 combustion is regulated by means of the apertures 0, which are left open or are closed, 

 according to the intensity or direction of the wind. The air enters at the lower row 

 and the -smoke escapes at the upper. 



For the complete transformation of wood into charcoal in these kilns it requires 

 from four to eight days, according to whether the wood is dry or green. Dry wood 

 produces a greater percentage of charcoal and of better quality than green wood. 

 When the combustion is completed, all the apertures are hermetically sealed by means 

 of bricks and clay and the kiln is allowed to cool thoroughly. The cooling requires 

 about four days. 



Each kiln holds from 25 to 27 cords of wood, or about 3,o50 cubic feet ; one cord 

 of wood produces about 50 bushels of charcoal. In consequence, each kiln yields on 

 an average 1,300 bushels of charcoal in 10 days. During each operation about two 

 gallons of creosote tar runs out at the lower part of the ground door, but no use is 

 made of it. The charcoal made in this way is of excellent quality and gives great 

 satisfaction. 



Tbe weight of one bushel of charcoal is about 14 pounds ; consequently there are 

 about 142i bushels of charcoal to the ton. 



Composition of ash. At the Leadville smelters charcoal is said to contain about 

 2.5 per cent, of ash. This figure is probably quite correct for pit-charcoal. A rough 

 examination was made of a fine jet black piece of charcoal from McAllister's kilns, 

 picked from the heap at Messrs. Billing & Eilers's smelter. This gave only 1.G2 per 

 cent, of ash, containing 0.42 per cent, of soluble salts (carbonate of potash and soda, 

 with some chlorides) and 1.20 per cent, of alumina, silica, lime, phosphates, etc. A 

 rough examination was also made of some charcoal ash found in the laboratory of the 

 Gumming & Finn smelter; the proportion of soluble alkaline salts was about the 

 same as in the preceding, but the insoluble residue was chiefly composed of alumina. 

 In all probability the composition of charcoal ash varies according to the nature of 

 the soil upon which the trees grew. In the discussion on smelting, 2.5 per cent, has 

 been adopted as the average percentage of ash in charcoal. 



Dolomites. The dolomites are extracted chiefly from theDugan and Montgomery 

 quarries and from the Glass- Pendery and Carbonate mines. The consumption, price, 

 and proportion of dolomite used, etc.; will be found in Table IV. The samples which 

 were analyzed in the laboratory of the Survey were prepared by mixing equal weights 

 of typical specimens picked up on the heap at various smelters. 



Analysis X is that of the Dugan dolomite from the Dugau quarry, near Mount 

 Zion, Arkansas Valley. This dolomite is in rather largo, indistinct crystals, with a 

 bluish-black tinge and'with white, creamy-yellow, and red spots. The specimens were 

 found at the Gumming & Finn and Elgin smelters. 



Analysis XI is that of the Montgomery dolomite, from the Montgomery quarry, 

 on Iron Hill, California gulch. This dolomite is in compact, homogeneous masses, with 

 a fine crystalline structure and a bluish-black tinge. The specimens were collected at 

 the American, California, Grant, Harrison, La Plata, and Billing & Eilers's smelters. 



Analysis XII is that of dolomite from the Glass- Pendery mine, on Carbonate Hill. 

 This dolomite has a very peculiar appearance. It is formed of homogeneous and very 



