Lightning, Ascending.
Lightning is sometimes observed which seems to ascend. It is thought
that this may be due to positive electrification of the earth and
negative electrification of the clouds.
Lightning, Globe or Globular.
A very unusual form of lightning discharge, in which the flashes appear
as globes or balls of light. They are sometimes visible for ten seconds,
moving so slowly that the eye can follow them. They often rebound on
striking the ground, and sometimes explode with a noise like a cannon.
They have never been satisfactorily explained. Sometimes the phenomenon
is probably subjective and due to persistence of vision.
Lightning Jar.
A Leyden jar whose coatings are of metallic filings dusted on to the
surface while shellacked, and before the varnish has had time to dry. In
its discharge a scintillation of sparks appears all over the surface.
Line of Contact.
The line joining the points of contact of the commutator brushes in a
dynamo or motor.
Synonym--Diameter of Commutation.
Lines of Force.
Imaginary lines denoting the direction of repulsion or attraction in a
field of force, q. v. They may also be so distributed as to indicate the
relative intensity of all different parts of the field. They are normal
to equipotential surfaces. (See Electro-magnetic Lines of
Force--Electrostatic Lines of Force--Magnetic Lines of Force.)
Lines of Induction.
Imaginary lines within a body marking the direction taken within it by
magnetic induction. These are not necessarily parallel to lines of
force, but may, in bodies of uniform agglomeration, or in crystalline
bodies, take various directions.
Synonym--Lines of Magnetic Induction.
Lines of Slope.
Lines in a field of force which mark the directions in which the
intensity of force in the field most rapidly falls away.
Links, Fuse.
Links made of more or less easily fusible metal, for use as safety
fuses.
Listening Cam.
In a telephone exchange a cam or species of switch used to connect the
operator's telephone with a subscriber's line.