are fully understood, and the time of the eclipse can be predicted within the fraction of a second, the

that Chaos was come again: afterwards learning the cause, they went out and beheld the stars around the Sun. It was thought and said by many, not untruly, that the king (Stephen) would not continue a year in the government."

Columbus made use of an approaching eclipse of the moon, which took place March 1, 1504, to relieve his fleet, then in great distress from want of supplies. As a punishment to the islanders of Jamaica, who refused to assist him, he threatened to deprive them of the light of the moon. At first they were indifferent to his threats, but "when the eclipse actually commenced, the barbarians vied with each other in the production of the necessary supplies for the Spanish fleet."

Among the Hindoos a singular custom is said to exist. When, during a solar eclipse, the black disk of our satellite begins slowly to advance over the sun, the natives believe that some terrific monster is gradually devouring it. Thereupon they beat gongs, and rend the air with screams of terror and shouts of vengeance. For a time their frantic

change from broad daylight to almost instantaneous gloom is overwhelming, and inspires with awe even the most careless observer. (See note, p. 303.)

The Saros.-The nodes of the moon's orbit are constantly moving backward. They complete a revolution around the ecliptic in about 18 years. Now the moon makes 223 synodic revolutions in 18 years and 10 days; the sun makes 19 revolutions with regard to the lunar nodes in about the same time. Hence, in that period, the sun, the moon, and the nodes will be in nearly the same relative position. If, then, we reckon 18 years and 10 days from any eclipse, we shall find the time of its repetition.

This method was discovered, it is said, by the Chaldeans. The ancients were enabled, by this means, to predict eclipses, but it is considered too inaccurate by modern astronomers.

Metonic Cycle.-The Metonic Cycle (sometimes confounded with the Saros) was not used for foretelling eclipses, but for ascertaining the age of the moon at a given period. It consists of nineteen tropical years,* during which time there are 235 new moons; so that, at the end of this period, the new moons will recur at seasons of the year corresponding to those of the preceding cycle. By registering, therefore, the exact days of any cycle at which the

efforts seem futile and the eclipse still progresses. At length, however, the increasing uproar reaches the voracious monster; he appears to pause, and then, like a fish rejecting a nearly swallowed bait, gradually disgorges the fiery mouthful. When the sun is quite clear of the great dragon's mouth, a shout of joy is raised, and the poor natives disperse, delighted to think that they have so successfully relieved their deity from his impending peril.

* A tropical year is the interval between two successive returns of the sun to the vernal equinox.

new and full moons occur, such a calendar shows on what days these events will happen in succeeding cycles.

Since the appointment of games, feasts, and fasts has been made very extensively, both in ancient and modern times, according to new or full moons, such a calendar becomes very convenient for finding the day on which the required new or full moon takes place. Thus, if a festival were decreed to be held in any given year on the day of the first full moon after the vernal equinox: find what year it is of the lunar cycle, then refer to the corresponding year of the preceding cycle, and the day will be the same. The Golden Number, a term still used in our almanacs, denotes the year of the lunar cycle. Four is the golden number for 1884.

K

Fig. 62.

Eclipse of the Moon.

An Eclipse of the Moon is caused by the passing of the moon into the shadow of the earth, and hence can take place only at full moon-opposition. As the moon's orbit is inclined to the ecliptic, her path is partly above and partly below the earth's shadow; thus an eclipse of the moon can take place only at or near one of the nodes. In Fig. 62, the umbra is represented by the space between the lines Kc and