Page:Book of knowledge (1).pdf/17

 rue conjunction; but if the meeting of the sun and either node happen at the very full moon, then he shall totally escape an eclipse of the new moon.

AN eclipse of the moon is nothing but her being deprived of the sun’s light by the interposition of the earth, betwixt the sun and her; which can never happen but when the moon is at full; nor doth it always happen then, because of her latitude, she will be eclipsed; but if the sum of the semidiameter of the moon and earth's shadow, at the time of the true full, be more than the moon’s latitude, she will be eclipsed; but if the sum of the semidiameter be less than the latitude, she cannot suffer an eclipse that full; and tho' at every full moon there is not an eclipse, yet she raerly passeth a year together without being eclipsed little or much, for the sun passeth her nodes every year.

TOTAL eclipses are such as quite cover the illuminated body, and are either central or not; central are when the centres of the sun, earth and moon are in a straight line; or when the centres of the sun, earth and moon coincide; not central, are when the centres do not coincide, though notwithstanding they may be total. Partial, are when the sun, moon or other luminous bodies are but partly darkened.

Now the moon being less than the earth, and the earth much less than the sun, solar eclipses are never or very rarely total; yet, if it happen, the moon in Perigaco, and the sun in Apogaco, an eclipse of the sun may be total; for then the moon's apparent diameter exceeds the sun’s considerably; and her quick and perfect shadow reaches the superfices of the earth, by which such places as are situated within the