IRON MANUFACTURE. 543 
In order to examine this working, the slag formation and fuel con- 
sumption, also the prooable heat distribution in the furnace, will be 
considered and compared with that of other furnaces. 
First, however, it will be well to make a few preliminary state— 
ments in regard to slags. The characters of the slag that concern the 
metallurgist are its fusibility and its fluidity. Combinations of silica, 
lime and alumina are fusible between very wide limits in composition, 
but they differ greatly, not only in the temperature at which they fuse, 
but in the character of the fusion, some melting immediately to a liquid 
which flows freely, some becoming gradually soft, and passing through 
all grades from hard to liquid. These two methods of melting may be 
illustrated by respectively the melting of tar and the melting of lead, 
one passing slowly from the solid to the liquid state, the other almost — 
instantly. As is well known, the slags of charcoal furnaces have the 
viscid character ; the composition accompanying this character is shown 
by the analysis made of slags from charcoal furnaces in the Hanging 
Rock region, published in this report. It will be seen that the per- 
centage of silica is high. In general, it may be stated, experiments 
have shown that slags in which the percentage of silica was high, had 
this character. | 
Slags from coke and coal furnaces have compositions illustrated by 
the following analysis: 
1 2 3. 4 
DUCA Mce sc csaisseascssticdssc ceccenvescitecolsidaees«ccseur 38.10 35.78 30.66 36.41 
Theva ie Ss heh a eal one a ee 16.00 | 11.69 13.75 | 12.88 
IDR GS CoS ONd CORD SRCOHEDADOD BORECR RUC CEOCE DORE RCC ore TEry 39.09 49.65 50.97 47.43 
INFAS MOS Are css secrete econ eet ie ee eek eset ebeks vadect 441 | 0.82 — 2.66 1.15 
ROLOKA MCT OMILOMG ee cccerecceeece stares tas eee eee .30 undet. undet. undet. 
Protoxide of Manganese...........ccecceeseseee ces 50 > .60 72 
PS UUM Teens cae ne owls siisisssinasnwaics eda seness ee undet. 1.55 2.21 1.68 
1. Cinder, Hocking Valley. 
Such slags melt differently, becoming suddenly liquid and solidi- 
fying with equal rapidity, so that in running from the furnace, crusts of 
