Another difficulty has to be noticed; classic literature does little or nothing to help us in filling up these voids and dissipating the obscurities they cause. The Greeks were guilty of many errors when they attempted to understand and describe foreign religions, but their relations with the Egyptians and Phoenicians were so prolonged, and, towards the end, so intimate, that at last they did succeed in grasping some of the doctrine taught in the sanctuaries of Heliopolis and Thebes, of Byblos and Hierapolis. With their lively intellects they could hardly frequent the temples, examine the sacred images, and question the priests as to the national rites and ceremonies without discovering at least a part of the truth. It was not so with Chaldaea. Babylon was too far off. Until the time of Alexander's conquests the boldest travellers did no more than glance into its streets and monumental buildings, and by that time Nineveh had long ceased to exist. It was only under the first of the Seleucidae, when a Macedonian kingdom was established in the centre of Mesopotamia, that the curiosity of the Greeks led them to make inquiries similar to those they had pursued for some three centuries in the valley of the Nile. We cannot doubt that this desire for information arose among the followers of those princes themselves; many of them were very intelligent men; and when Berosus determined to write his history in Greek, he may have wished to answer the questions asked in his hearing by the Greek writers and philosophers; by those Alexandrians who were not all at Alexandria. Unfortunately, nearly the whole of his work has been lost. At the end of a century and a half Babylon shook off Hellenism, and Mesopotamia fell into the hands of the Parthians. These people affected, in some degree, the poetry and arts of Greece, but at bottom they were nothing more than Oriental barbarians. Their capital, Ctesiphon, seems never to have attracted learned men, nor ever to have been a seat of those inquiries into the past of the older races in which the cultured cities of the Greek world took so great a pleasure. When Rome became the heir of Greece and the perpetuator of her traditions, we may believe that, under Trajan, she set about establishing herself in the country; but she soon found it necessary to withdraw within the Euphrates, and it was her loss when the Parthians fell from power to be succeeded in the lordship of Mesopotamia by the Sassanids.[82]