Contraction for Indian Wire Gauge–the gauge adopted in British India.

Having equal properties in all directions; the reverse of anisotropic,
q. v. Thus a homogeneous mass of copper or silver has the same specific
resistance in all directions and is an isotropic conductor. Glass has
the same specific inductive capacity in all directions and is an
isotropic medium or dielectric. The same applies to magnetism. Iron is
an isotropic paramagnetic [...]

The system of supplying electric energy by independent generating
systems, dynamo or battery, for each house, factory or other place, as
contra-distinguished from Central Station Distribution or Supply.

A map showing the isogonic lines. On such a map each line is
characterized and marked with the degrees and direction of variation of
the compass upon itself.
Synonym–Declination Map.

[Transcriber's note: The file Earth_Declination_1590_1990.gif provided
by the U.S. Geological Survey (http://www.usgs.gov) is an animation of
the declination of the entire earth.]

Lines on a map marking the locus of or connecting those points where the
declination or variation of the magnetic needle is the same. (See
Magnetic Elements–Declination of Magnetic Needle.)
Synonyms–Isogonal Lines–Halleyan Lines.

A map showing the position of isodynamic lines. (See Poles of
Intensity.)

Lines marking the locus of places of equal magnetic intensity on the
earth’s surface. (See Magnetic Elements, Poles of Intensity.)

A map showing the position of isoclinic lines.

The lines denoting the locus of sets of equal dips or inclinations of
the magnetic needle upon the earth’s surface, the magnetic parallels, q.
v. These lines are very irregular. (See Magnetic Elements.)

Equality of periodic time; as of the times of successive beats of a
tuning fork, or of the times of oscillations of a pendulum.