They have left some trace of their handiwork, for the whole extent of the desert is studded with gigantic _tels_ spaced six or seven miles apart--huge mounds of earth as big as Silbury Hill. What purpose these can have originally served is a matter of much conjecture. Possibly they were sepulchral tumuli, possibly the mounts of village castles, possibly high places for the performance of sacrificial rites; but in any case it is evident that they cannot have been erected without a vast amount of human labour, and that the whole of the present population would not suffice to raise one. Now they serve chiefly as landmarks by which the faintly marked road can steer its course towards the horizon; and in several instances they still form burial places, possibly from some vague feeling that they must have been sacred long ago. The more direct southerly road from the Euphrates ferry to Mosul traverses this desolate region for a journey of fully ten days; but the three or four days extra entailed by the divergence through Diarbekr bring with them their own compensation in the shape of greater interest on the way. Moreover the _Chôl_ has its dangers. In summer it is a veritable furnace, and tall awe-inspiring dust devils stalk about it like wandering Jann. But the chief terror of travellers is the "Poison Wind" or _Sâm_, a faint invisible eddy of scorching air, which will pick out a single man or beast from the midst of a caravan and strike him down instantly senseless, sometimes even killing him on the spot. At the other end of the scale the district is not exempt from blizzards. In the extraordinarily severe winter of 1910-1911 the northern part of the _Chôl_ was visited by a prodigious snowstorm--a most unusual phenomenon--and many parties of Arabs were positively snowed under in their encampments and perished of cold and hunger before they were able to extricate themselves.[36] A wandering Kurd related to us how he had stumbled on such a camp after the visitation was over. His suspicion that something was amiss was first aroused by the fact that he encountered no challenge either from man or dog. When he came to the tents he found them full of dead bodies. The only living creatures among them were one old woman and a mare. Feeling sure that the old woman must die in any case he only brought the mare away with him; "but she died too," he said plaintively, "before I could get her to my camp."