At an earlier period, Polybius (204-122 B.C.) wrote to explain to the Greeks how the power of the Romans had established itself in Greece. His great work was a universal history, but of the forty books of which it consisted only five have been preserved; perhaps no historical work has ever been written with such definiteness of purpose or unity of plan, or with such self-consciousness on the part of the writer. The object to which he directs attention is the manner in which fortune or providence uses the ability and energy of man as instruments in carrying out what is predetermined, and specially the exemplification of these principles in the wonderful growth of the Roman power during the fifty-three years of which he treats. Taking his history as a whole, it is hardly possible to speak in too high terms of it, though the style has many blemishes, such as endless digressions, wearisome repetition of his own principles and colloquial vulgarisms. Diodorus, a native of Sicily, generally known as the Sicilian (Siculus), flourished in the time of the first two Caesars. In his great work, the "Historical Library," it was his object to write a history of the world down to the commencement of Caesar's Gallic wars. He is content to give a bare recital of the facts, which crowded upon him and left him no time to be diffuse or ornamental. The geography of Strabo (fl. 10 A.D.), which has made his name familiar to modern scholars, has come down to us very nearly complete. Its merits are literary rather than scientific. His object was to give an instructive and readable account of the known world, from the point of view taken by a Greek man of letters. His style is simple, unadorned, and unaffected. Plutarch (40-120 A.D.) may be classed among the philosophers as well as among the historians. Though he has left many essays and works on different subjects, he is best known as a biographer. His lives of celebrated Greeks and Romans have made his name familiar to the readers of every country. The universal popularity of his biographies is due to the fact that they are dramatic pictures, in which each personage is represented as acting according to his leading characteristics. Pausanias (fl. 184 A.D.), a professed describer of countries and of their antiquities and works of art, in his "Gazetteer of Hellas" has left the best repertory of information for the topography, local history, religious observances, architecture, and sculpture of the different states of Greece.