the
account is not as full as I could have wished, yet it is hoped that
from the description of such experiments as relate to the salient
features, followed by a summary of their bearings upon the research,
and the conclusions at which we have arrived, a fair idea may be
gathered of this research.
One reason for writing this paper at the present time has been a publication on the same subject by Otto Ruff in Zeitschrift fur Anorganische Chemie, Vol.
xcix, pp. 73-104, May 25th, 1917, who also referred to the work of
Lummer on the apparently molten aspect of the surface of the carbon of
the electric arc.
In
my paper to the Royal Society in 1888 were described experiments where
a carbon rod heated by a current of electricity (Fig. 1) was im-
