IDELER, CHRISTIAN LUDWIG German chronologist and astronomer, was born near Perleberg on Sept. 21, 1766. He became professor at the university of Berlin in 182I, and 18 years later foreign member of the Institute of France. From 1816 to 1822 he was tutor to the young princes William Frederick and Charles. He died in Berlin on Aug. Io, 1846. He devoted his life chiefly to the examination of ancient systems of chronology. In 1825-26 he published his great work, Handbuch der mathematischen and technischen Chronologie ( 2 vols.; end ed., 1883), re-edited as Lehrbuch der Chronologie (1831) ; a supplementary volume, Die Zeitrechnung der Chinesen, appeared in