Diophantus Of Alexandria, the only Greek writer on algebra, first mentioned by John, patriarch of Jerusalem, in the 8th century, unless he be identical with the astronomer Dio-phantus, on whose work Hypatia is said by Suidas to have written a commentary. There are no more definite indications of his era. When his MSS. came to light in the 16th century, thirteen books of his were announced, only six of which have been produced. Another treatise by him, IIepi

(" On Polygonal Numbers"), is extant. These books contain a system of reasoning on numbers with the use of general symbols, and are therefore algebraical treatises, though the demonstrations are written out at length in common language. The term Dio-phantine was applied by some modern mathematicians to the peculiar analysis employed in investigating the theory of numbers. The similarity of the Diophantine and Hindoo algebra renders it probable that they had a common origin, or that one was derived from the other. The best edition of his works is that of Fermat, in Greek and Latin (Toulouse, 1670). They were translated into German by Schulz (Berlin, 1821). The six books of the " Arithmetic " were translated into French by Stevin and Girard (Paris, 1625).