Analyses of Stourbridge Clay. 
Sillca. 
Alumina. 
Peroxide Iron. 
Alkalies, loss, 
etc. 
1, 
2 
3 
4 
5, 
6 
7 
8, 
9, 
66.47 
65.65 
65.50 
67.00 
63.42 
65.08 
65.21 
58.48 
63.40 
26.26 
26.59 
27.35 
25.80 
31.20 
27.39 
27.82 
35.78 
31.70 
6.63 
5.71 
5.40 
4.90 
4.70 
3.98 
3.41 
3.02 
3.00 
.64 
2.05 
1.75 
2.30 
.68 
3.55 
3.56 
2.72 
1.90 
. — ■— '. 
Limit. Grover very justly points out " that the infusibil- 
ity of any substance depends not merely upon the Chem 
ical nature of its constituents, but also upon the manner 
in which those constituents are combined with one another. 
For example, granite per se is infusible at ordinary high 
temperatures, whilst pounded granite can bo rcadily melted 
by the same degree of heat. Thus it would seem that a 
porosity in structure, brought about by a coarseness of ele- 
mentary particles, would enhance the chemical infusibility 
of a material; and that in fire-clay goods a close uniform 
structure, though pleasing to the eye, is not favorable to 
their refractory powers, since the component particles 
should have a facility for contraction or expansion under 
hiffh temperature, and the air cavities act as valuable non- 
conductors of heat. Hence it will be evident that to deter- 
mine accurate conclusions respecting these wares, a fire 
fest is as essential as chemical aualysis.