Luminous streams of the molecules are produced by electric high
potential discharges between electrodes. The course of the discharge is
normal, in general terms, to the surfaces of the electrodes, and reaches
from one to the other in a curve or straight line, as the case may be.
These luminous streams are deflected by a magnetic field; if brought to
a focus can heat refractory material in that focus to a full white heat,
and can develop phosphorescence. The latter is termed electric
phosphorescence. A great variety of experiments have been devised to
illustrate the phenomena of radiant matter. The vacuum is generally
produced in a hermetically sealed glass vessel into which the electrodes
are sealed, and which contain the phosphorescent substances or other
essentials for the experiments. The vessels are termed Crookes' Tubes.
[Transcriber's note: Crookes reported on "radiant matter" in 1879. It is
actually electrons, but he failed to distinguish them from ordinary
atoms. Thompson properly described electrons in 1897.]
Matteueci's Experiment.
An experiment for showing the inductive effect of the discharge of a
Leyden jar. Two glass plates are supported on standards in a vertical
position. Flat coils of wire are wound or coiled and secured to one
surface of each plate. One plate has much finer and longer wire than the
other. Metal handles are connected to the ends of the coarser wire coil.
The plates are placed with their coils facing each other. A Leyden jar
is discharged through the coarser coil, while the handles are grasped by
a person. The shock of the discharge is felt by him.
Matting, Electric Floor.
Matting or floor covering underlaid with burglar alarm contacts, so
arranged as to be closed by anyone walking on the matting. The contacts
are connected to a burglar alarm system. The object is to provide an
alarm if a burglar enters a house, in case he should enter a door or
window without sounding the bell. The latter can be done by cutting out
the window or part of the door instead of opening it.
Maxwell's Theory of Light.
A theory of light. It is due to J. Clerk Maxwell.
It supposes the phenomena of electric induction to be due to the ether,
q. v. It supposes the condition of the ether when conveying light to be
the same as if exposed to the induction of rapidly alternating currents
or discharges (in this case synonymous). It therefore is an
electro-magnetic effect if the theory is correct.
An electric stress such as one due to the induction of an
electrostatically charged body is not a wave-creating element or factor,
but is a simple stress. But let this stress be stopped and renewed and
at once it appears as a wave-forming agency.
This stoppage and renewal represents evidently a discharge succeeded by
a charge, or if repeated is equivalent to an intermittent current or an
alternating one.