2j6 Mr . T. Wedgwood's Experiments and Observations 
EXPERIMENT VI. 
A tube of unglazed earthen ware, open at top, and having 
one half of its bottom blackened on the outside, was placed in 
a red hot crucible, and the eye directed, as before, to the in- 
side : the part which was externally blackened became always 
red before the other. 
The experiment was repeated with a metalline tube ; but 
no difference could here be perceived between the blackened 
and unblackened half of the bottom. The reason is obvious, 
from the foregoing observations. 
EXPERIMENT VII. 
To ascertain whether metals and earthy bodies begin to shine 
at the same temperature, I gilded, in lines running across, a 
thin piece of earthen ware, of the specific gravity of about 
2,000, and luted it to the end of a tube, the gilt side being 
inwards ; then, directing my eye into the tube, I held it 
within a crucible, which was gradually made red hot ; but I 
could not, after many trials, perceive that either the gold or 
the earthen ware began to shine first. 
As it appears, from this experiment, that gold and earthen 
ware begin to shine at the same temperature ; and as no two 
bodies can well be more different, in all their sensible proper- 
ties, may it not be inferred, that almost all bodies begin to 
shine at the same temperature ? 
EXPERIMENT VIII. 
Observing that colourless transparent glass had a paler hue, 
when red hot, than most other bodies, I conceived that it might 
