the office or dignity of caliph; See the preceding article. The successions of caliphs continued from the death of Mahomet till the 655th year of the Hegira, when the city of Bagdad was taken by the Tartars. After this, however, there were persons who claimed the caliphate, as pretending to be of the family of the Abbasides, and to whom the sultans of Egypt rendered great honours at Cairo, as the true successors of Mahomet; but this honour was merely titular, and the rights allowed them only in matters relating to religion; and though they bore the sovereign title of caliph, they were nevertheless subjects and dependents of the sultans. In the year of the Hegira 361, a kind of caliphate was erected by the Fatemites in Africa, and lasted till it was suppressed by Saladin. Historians also speak of a third caliphate in Yemen or Arabia Felix, erected by some princes of the family of the Jobites. The emperors of Morocco assume the title of grand chieftain; and pretend to be the true caliphs, or successors of Mahomet, though under another name.

CALIPPIC period, in Chronology, a series of seventy-five Calippic period seventy-six years, perpetually recurring; which clasped, 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 $365\frac{1}{4}$ days, $6h.\ 18'56''\ 50\frac{3}{4}''\ 41\frac{1}{4}'\ 34\frac{1}{2}''$; and the lunar month, $29d.\ 12h.\ 45'\ 47''\ 26\frac{3}{4}'\ 48\frac{3}{4}'\ 35\frac{1}{2}''$. But Calippus, considering that the Metonic quantity of the solar year was not exact, multiplied Meton's period by 4, and thence arose a period of 76 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 4384th of the Julian period. It is demonstrated, however, that the Calippic period itself is not accurate; that it does not bring the new and full moons precisely to their places; $8h.\ 5'52''\ 6s''$, being the excess of $940$ lunations, above 76 solar years; but brings them too late, by a whole day in 225 years.