those as varieties of the same class, which are altered by 
the proportion of the second and third mixtures. Again 9 
each of these varieties are susceptible of a multiplicity of 
modifications before an earth is so far diminished as to 
give an ascendency to another, or before the third rank of 
proportion has assumed that of the second or first,, The 
simple combination of the earths, and their degrees of pre- 
dominancy, may be thus arranged 
1st Variety, 
{ Iron 
Lime 
Silex - 
f Iron 
Calcareous iron-stone < £™. e 
Silex - 
f Iron 
. Silex - 
Siliceous iron-stone < Lime 
Clay - 
2d Variety. 
- Iron 
- Clay 
- Silex 
■ Lime 
Lon 
• Lime 
Silex 
Ciay 
Iron 
Silex 
Clay 
Lime 
,0 * , 
<u 
S* 02 
b> > CS 
2 CT' 
a <y> 
o 
<-> © 
V3 
o JS 
cfl O 
£ o 
t/5 
To assay any of these varieties, a flux peculiar to the 
nature of the mixture is necessary 5 so that the changes 
of proportion in the solvent ought to extend to seven, in- 
cluding the class of equalised mixtures, in order that the 
precise same quality of crude iron may be produced from 
all the varieties of iron-stone, Tire modification of each 
variety will be found to be sufficiently accurate, if assayed 
by the flux peculiar to itself, The arrangement of the 
three classes of ores into two varieties, each forming a 
distinct stage of combination, indicated by the predomi- 
nancy of the first and second earth, are, with the neutral 
class, sufficiently minute for any purpose in the assay-fur- 
nace, and are sufficient to form an accurate and extensive 
knowledge of the analogy of these results with those in th& 
blast-fumace. 
Q 
