in Chronology, a series of seventy-six years, perpetually recurring; which being elapsed, the middle of the new and full moons, as its inventor Calippus, an Athenian, imagined, return to the same day of the solar year. Meton, a hundred years before, had invented the period or cycle of nineteen years, assuming the quantity of the solar year to be $365\frac{1}{4}$ days; and that of the lunar month $29\frac{1}{2}$ days; but Calippus, considering that the Metonic quantity of the solar year was not exact, multiplied Meton's period by four, and thence arose a period of seventy-six years, called the Calippic. The Calippic period, therefore, contains $27,759$ days; and since the lunar cycle contains $235$ lunations, and the Calippic period is quadruple of this, it contains $940$ lunations. This period began in the third year of the 112th Olympiad, or the 4834th of the Julian period. It may be demonstrated, however, that the Calippic period itself is not accurate, and that it does not bring the new and full moons precisely to their places; $8h.\ 5m.\ 52s.\ 60^{\circ}$ being the excess of $940$ lunations above seventy-six solar years; but brings them too late by a whole day in $225$ years.