a celebrated mathematician of Alexandria, the reputed inventor of algebra. His era is uncertain. Some have placed him before Christ, and some after, in the reigns of Nero and the Antonines, but all with equal uncertainty. It is doubtful whether or not he be the same Diophantus who wrote the Canon Astronomicus, which Suidas says was commented on by the celebrated Hypatia, daughter of Theon of Alexandria. By the ancients, he was ranked with Pythagoras and Euclid in mathematical learning. From his epitaph in the Anthologia, Bachet has gleaned the following particulars concerning him, namely, that he was married when he was thirty-three years old, and had a son born five years thereafter; that this son died at the age of forty-two, and that his father did not survive him above four years. From this it appears that Diophantus lived to the age of eighty-four. See Algebra.

DIOPTASE of Moss; the rhombohedral emerald malachite of Moss. This is a very rare mineral. It occurs in crystals of small dimensions, of a brilliant emerald-green