of this subject, accounts for all these variations, seeing that even the Persian writers themselves do not agree as to what is the length of their _schæni_ and _parasangæ_, each assigning to them a different length. When the Euphrates ceases, by running in its channel, to afford protection[539] to those who dwell on its banks, which it does when it approaches the confines of Charax, the country is immediately infested by the Attali, a predatory people of Arabia, beyond whom are found the Scenitæ.[540] The banks along this river are occupied by the Nomades of Arabia, as far as the deserts of Syria, from which, as we have already stated,[541] it takes a turn to the south,[542] and leaves the solitary deserts of Palmyra. Seleucia is distant, by way of the Euphrates, from the beginning of Mesopotamia, eleven hundred and twenty-five; from the Red Sea, by way of the Tigris, two hundred and twenty; and from Zeugma, seven hundred and twenty-three, miles. Zeugma is distant from Seleucia[543] in Syria, on the shores of our sea, one hundred and seventy-five[544] miles. Such is the extent of the land that lies in these parts between the two seas.[545] The length of the kingdom of Parthia is nine hundred and eighteen miles. CHAP. 31.—THE TIGRIS. There is, besides the above, another town in Mesopotamia, on the banks of the Tigris and near its confluence with the Euphrates, the name of which is Digba.[546] (27.) But it will be as well now to give some particulars respecting the Tigris itself. This river rises in the region of Greater Armenia,[547] from a very remarkable source, situate on a plain. The name of the spot is Elegosine,[548] and the stream, as soon as it begins to flow, though with a slow current, has the name of Diglito.[549] When its course becomes more rapid, it assumes the name of Tigris,[550] given to it on account of its swiftness, that word signifying an arrow in the Median language. It then flows into Lake Arethusa,[551] the waters of which are able to support all weighty substances thrown into them, and exhale nitrous vapours. This lake produces only one kind of fish, which, however, never enter the current of the river in its passage through the lake: and in a similar manner, the fish of the Tigris will never swim out of its stream into the waters of the lake. Distinguishable from the lake, both by the rapidity and the colour of its waters, the tide of the river is hurried along; after it has passed through and arrived at Mount Taurus, it disappears[552] in a cavern of that mountain, and passing beneath it, bursts forth on the other side; the spot bears the name of Zoroande.[553] That the waters on either side of the mountain are the same, is evident from the fact, that bodies thrown in on the one side will reappear on the other. It then passes through another lake, called Thospites, and once more burying itself in the earth, reappears, after running a distance of twenty-two miles, in