ig. 3), surrounded by a primary spiral, was contained in a bell
jar, and when the pressure of air in the jar was about that of the
atmosphere the secondary discharge occurred in the bulb, as is
ordinarily the case. On exhausting the jar, however, the luminous
discharge grew fainter, and a point was reached at which no secondary
discharge was visible. Further exhaustion of the jar caused the
secondary discharge to appear outside the bulb. The fact of obtaining
no luminous discharge either in the bulb or jar the author could only
explain on two suppositions, viz., that under the conditions then
existing the specific inductive capacity of the gas was very great, or
that a discharge could pass without being luminous. The author had
also observed that the conductivity of a vacuum tube without
electrodes increased as the pressure diminished until a certain point
was reached, and afterward diminished again, thus showing that the
high resistance of a nearly perfect vacuum is in no way due to the
presence of the electrodes. One peculiarity of the discharges was
their local nature, the rings of light being much more sharply defined
than was to be expected. They were also found to be most easily
produced when the chain of molecules in the discharge were all of the
same kind. For example, a discharge could be easily sent through a
tube many feet long, but the introduction of a small pellet of mercury
in the tube stopped the discharge, although the conductivity of the
mercury was much greater than that of the vacuum. In some cases he had
noticed that a very fine wire placed within a tube on the side remote
from the primary circuit would prevent a luminous discharge in that
tube.

[Illustration: FIG. 4.--Exhausted Secondary Coil of One Loop
Containing Bulbs. The discharge passed along the inner side of the
bulbs, the primary coils being placed within the secondary.]

* * * * *

THE ELECTRICAL MANUFACTURE OF PHOSPHORUS.

Dr. Readman, at the May meeting of the Glasgow Section of the Society
of Chemical Industry, gave a description of the new works and plant
which have been erected at Wolverhampton for the manufacture of
phosphorus by the Readman-Parker patents. The process consists in
decomposing the mixture of phosphoric acid, or acid phosphates and
carbon, by the heat of the electric arc embedded in the mass.

* * * * *

LAYING A MILITARY FIELD TELEGRA