The Story of Electricity

by John Munro

APPENDIX.

UNITS OF MEASUREMENT.

(From Munro and Jamieson's Pocket-book of Electrical Rules and
Tables).

I. FUNDAMENTAL UNITS.—The electrical units are derived from the following mechanical units:—

The Centimetre as a unit of length;
The Gramme as a unit of mass;
The Second as a unit of time.

The Centimetre is equal to 0.3937 inch in length, and nominally represents one thousand-millionth part, or 1/1,000,000,000 of a quadrant of the earth.

The Gramme is equal to 15.432 grains, and represents the mass of a cubic centimetre of water at 4 degrees C. Mass is the quantity of matter in a body.

The Second is the time of one swing of a pendulum making 86,164.09 swings in a sidereal day, or 1/86,400 part of a mean solar day.