Several learned Antiquaries have attempted to ascertain the beginning of the Parthian Epocha, which so often occurs on the Parthian coins of a later date. The empire of the Arsacidae extended from the Indus to the Euphrates, and from the Caspian Sea to the Persian Gulph and the Indian Ocean; and their power often gave umbrage to the Romans, though sovereigns of all the known and civilized part of our globe. Their coins had a currency in a great part of Asia; and, as they frequently had Greek inscriptions sometimes with epocha's, it has been a subject of enquiry among the most skilful Antiquaries to explain these coins, and ascertain the Parthian Epocha. Vaillant, Longuerue, Bayer, Froelich, Pellerin, and Swinton, have among others applied themselves to this inquiry. As they have exhausted their extensive reading and learning in support of their respective opinions on this subject, it cannot be expected that any thing curious or new should be said by a later writer. All therefore that I can promise in this memoir, is a new argument in support of the opinion that the Epocha of the Arsacidae began in the year 256, before the Christian Epocha, or in the 498th year after the foundation of Rome.