Dionysius Cassius, a celebrated Greek critic and grammarian, was, according to Fabricius, grandson of Cassius Longinus, who is mentioned by Plutarch (Symp. ix. 1); but this is a mere conjecture, unsupported by any adequate proof. The precise period of his birth is unknown, though it is not unlikely that it took place about A.D. 213, in the reign of Caracalla, as he may be supposed to have preceded by at least twenty years his pupil Porphyry, who was born A.D. 233. There is no doubt that his death took place A.D. 273, when the Emperor Aurelian took Palmyra. The place of his birth is also a matter of much uncertainty, as it is nowhere distinctly stated. The circumstance of his understanding the Syrian language, and his uncle being from Emesa in Syria, has caused some to fix on that city as his native place; and others have suspected, though with still less appearance of probability, that he was from Palmyra. His uncle Fronto enjoyed considerable reputation as a teacher of philosophy at Athens; and, amongst other pupils, he had Philostratus, who is known to us by his life of the philosopher and prophet Apollonius of Tyana, which is still preserved. It would appear that Fronto was much attached to his nephew, whom he made his heir; and from him Longinus most probably derived the rudiments of his education. In his earlier years we find, from a fragment of one of his works preserved by Porphyry in his life of Plotinus, that he travelled much, and enjoyed the opportunity of becoming acquainted with all the most distinguished philosophers of his time. He gives the names of upwards of twenty, but, with the exception of Ammonius Saccas, Origen, Plotious, and Amelius, their celebrity was not sufficient to rescue them from oblivion. Ammonius taught the Platonic philosophy at Alexandria in Egypt, and at this time appears to have enjoyed a high reputation. The doctrines