In the most southerly group of desert routes between Syria and Mesopotamia Palmyra lies at the cross-roads. The north-eastward route from Damascus to Circesium is crossed by the eastward route from Emesa, now Homs, to Babylonia. Palmyra owes this key-position first to its precious springs and secondly to the fact that here the natural traffic lines from west to east debouch from the Syrian mountains into the head of the eastwardlooking basin of the Wadi el Khorr, a winter tributary of the Euphrates. Nor were these obvious routes the sole possibility. At Circesium the Euphrates may be crossed: at its eastward turn the lower river and its valley-dwellers become dominant—here runs the modern frontier between Syria and Iraq. Avoiding this control, caravan routes, negotiable solely by those with intimate knowledge of the waste and its people, lead direct to the heart of Mesopotamia and onwards to the Persian Gulf. As between East and West, Palmyra, an island in the desert, offered both a mart for exchange and an essential staging-point for direct through traffic. Its possessors were by nature masters of the situation; and, while they might be subject to the cultural or political influences of either East or West, their geographical isolation secured for them an independence founded upon pre-eminent experience of desert ways, which constituted them the natural masters and middlemen of the caravan routes that met and branched or crossed in their oasis.
Distribution of ascidians Phallusia nigra (Tunicata: Ascidiacea) on the north coast of the Persian Gulf, Iran – RETRACTION