Molecular Rigidity.
The tendency of the molecules of a mass to retain their position in a
mass in resistance to polarizing or depolarizing force, the first being
the effect of a magnetic field. It is the theoretical cause of coercive
force, q. v., and of residual magnetism. (See Magnetism, Residual.)
Molecule.
The smallest particle of matter that can exist alone. It is made up of
atoms, but an atom can never exist alone, but only, with one or two
possible exceptions, combined with one or more other atoms as a
molecule. The molecules under present conditions are not in constant
contact with each other, but are perpetually vibrating through paths, in
solids probably in defined paths, in liquids and gases in perpetually
new paths. The molecules collide with each other and rebound. This
motion is the kinetic motion termed heat. At the absolute zero--minus
273.72° C. (-460.7° F.) the molecules would be in contact and quiescent.
In the gaseous state the molecules of most substances occupy the same
volume; those of a few elements occupy one-half and of others twice the
normal volume. The mean free path of the molecule of hydrogen is about
1/20,000 mm. (1/508,000 inch) (Maxwell) or twice this length (Crookes),
the collisions in hydrogen are about 17,750 millions per second; the
diameter is about 8/10,000,000 mm. (8/254,000,000 inch) ; A particle of
matter 1/4,000 mm. (1/102,000 inch) contains, it is supposed, about
40,000 molecules. The results of different authorities vary so widely as
to deprive the subject of much of its interest. A Sprengel pump, such as
used for exhausting Geissler tubes, or incandescent lamp bulbs, may
leave only one hundred-millionth (1/100,000,000,) of an atmosphere
present, giving the molecules a capability of an average free path of
vibration 33 feet long.
Moment.
When a force is applied so as to tend to produce rotation around a
point, the product of the force by the shortest distance from the point
of rotation to the extension of the line of the force. Such distance is
the perpendicular to the extension of the line through the point of
rotation.
Mordey Effect.
A phenomenon observed in dynamo armatures. At full loads the hysteresis
decreases. The effect is thus expressed by S. P. Thompson. "When an
armature core is rotated in a strong magnetic field, the magnetization
of the iron is being continually carried through a cycle, but in a
manner quite different from that in which it is carried when the
magnetizing force is periodically reversed, as in the core of a
transformer. Mordey has found the losses by hysteresis to be somewhat
smaller in the former case than in the latter."
Morse Receiver.
The receiving instrument formerly universally used in the Morse system.
It is now but little employed, the sounder having displaced it. Several
types were invented.
It consists of machinery which carries a reel of paper ribbon arranged
to be fed over a roller by clockwork. A pencil, inking roller, or
embossing stylus (for the latter the roller must have a groove) is
carried by an arm with restricted range of vibration just over the paper
and roller. The armature of an electro-magnet is attached to the arm.
When the magnet is excited the armature is attracted and the marking
device is pressed on the paper. If the clockwork is in operation the
marker will make a line as long as the armature is attracted. When
released no mark will be produced. In this way the dots and dashes of
the Morse code are made on a ribbon of paper.
As an inking arrangement a small roller is carried by the end of the
vibrating arm. The embosser, or dry point stylus, was very extensively
used. The clockwork was generally driven by descending weights.
Synonym--Morse Recorder.