Iron o 
209 
productive of a surface deeper in the curve, and rougher, 
with additional asperities, The contrary is the case : 
when crude iron is so far debased as to be run from 
the furnace in clotted lumps highly oxygenated, the sur- 
face of the pigs is found to be more convex than that of 
No. 1. iron ; but then the fracture of such metal presents 
|j an impure mass covered on both faces with a mixture of 
oxydated iron, of a blueish colour, nearly metallic. In 
short, this quality of iron is incapable of receiving such a 
degree of fluidity as to enable us to judge whether the con- 
vexity of its surface is peculiar to its state, or is owing to 
| its want of division as a fluid, whereby the gradual conso 
lidation of the metal is prevented. 
| These features sufficiently distinguish betwixt the va~ 
j rious qualities of crude iron after they are obtained from 
the blast-furnace : there are, however, criterias not less 
infallible, whereby we can prejudge the quality of the 
metal many hours before it is run from the furnace. These 
J are the colour and form of the scoria, the colour of the 
I vitrid crust upon the working bars, and the quantity of 
| carburet which is attached to it. The variety of colour 
! and form in the cinder almost universally indicate the qua- 
lity of the metal on the hearth. Hence, from a long 
course of experience, have arisen the following denomi- 
nations : “ Cinder of sulphury iron “ Cinder of No. L 
No. 2, and No. 3 and u Cinder of ballast iron.’ 5 Al- 
though at different works, from local circumstances, the 
same kind of scoria may not indicate precisely the same 
quality of iron, yet the difference is so small that the fob 
lowing description of the various cinders may convey a 
very just idea of their general appearance. 
When the scoria is of a whitish colour and short form, 
branching from the notch of the dam, and emitting from 
its stream beautiful sparks of ignited carbon, resembling 
those ejected from a crucible of cast steel in fusion, ex- 
