Equatorial telescope. A telescope so mounted that its principal axis is parallel with the axis of the earth and moved by clockwork so that it will follow a star.
Evening Star. A planet which can be seen in the west just after the sun sets.
Fixed. (1) Fastened securely. (2) The stars are called fixed because they never seem to change their positions.
Forecast. A prediction of some future event. A forecast may be founded on fancy or on fact. A horoscope of a person is a forecast based on the fancy of an astrologer. A weather forecast is founded on the action of a barometer, and even then the forecast is uncertain enough. Forecasts of the time of eclipses, the return of comets and the like are founded on cold scientific facts and hence come true at exactly the calculated time.
Frequency. How often an event occurs.
Gas. That form of matter which is like air. Some gases remain in the gaseous state at ordinary temperatures. Gases have a tendency to expand without limit. See Vapor.
Generate. To produce. To set up; as a battery generates a current; the Sun generates power.
Gravitation. The force which attracts all bodies near the Earth to it and all bodies to each other.
Heavens. The sky. The space as far as the eye can see about the Earth. The space in which the stars and their planetary systems move.
Horizontal. [See Fig. 185].