By a quarter to four we were in the saddle, going down Wadi Diraa, into steep and high ridges of shifting sand, sometimes with a cap of harsh red rock jutting from them. After a while, three or four of us, in advance of the main body, climbed a sand-peak on hands and knees to spy out the railway. There was no air, and the exercise was more than we required; but our reward was immediate, for the line showed itself quiet and deserted-looking, on a green flat at the mouth of the deep valley down which the rest of the company was marching circumspectly with ready weapons.

We checked the men at the bottom of their narrow sand-fold, whilst we studied the railway. Everything was indeed peaceful and empty, even to the abandoned blockhouse in a rich patch of rank grass and weeds between us and the line. We ran to the edge of the rock-shelf, leaped out from it into the fine dry sand, and rolled down in a magnificent slide till we came to an abrupt and rather bruising halt in the level ground beside the column. We mounted, to hurry our camels out to the grazing, and leaving them there ran over to the railway and shouted the others on.

This unmolested crossing was blessed, for Sharraf had warned us seriously against the enemy patrols of mule-riding infantry and camel corps, reinforced from the entrenched posts by infantry on trolleys mounting machine-guns. Our riding-beasts we chased into the grass to feed for a few minutes, while the heavy camels marched over the valley, the line, and the farther flat, till sheltered in the sand and rock mouths of the country beyond the railway. Meanwhile the Ageyl amused us by fixing gun-cotton or gelatine charges about our crossing-place to as many of the rails as we had time to reach, and when our munching camels had been dragged away into safety on the far side of the line, we began, in proper order, to light the fuses, filling the hollow valley with the echoes of repeated bursts.

Auda had not before known dynamite, and with a child’s first pleasure was moved to a rush of hasty poetry on its powerful glory. We cut three telegraph wires, and fastened the free ends to the saddles of six riding-camels of the Howeitat. The astonished team struggled far into the eastern valleys with the growing weight of twanging, tangling wire and the bursting poles dragging after them. At last they could no longer move. So we cut them loose and rode laughing after the caravan.

For five miles we proceeded in the growing dusk, between ridges which seemed to run down like fingers from some knuckle in front of us. At last their rise and fall became too sharp to be crossed with safety by our weak animals in the dark, and we halted. The baggage and the bulk of our riders were still ahead of us, keeping the advantage they had gained while we played with the railway. In the night we could not find them, for the Turks were shouting hard and shooting at shadows from their stations on the line behind us; and we judged it prudent to keep quiet ourselves, not lighting fires nor sending up signals to attract attention.

However, ibn Dgheithir, in charge of the main body, had left a connecting file behind, and so before we had fallen asleep, two men came in to us, and reported that the rest were securely camped in the hidden fold of a steep sand-bank a little further on. We threw our saddle-bags again across our camels, and plodded after our guides in the murky dark (to-night was almost the last night of the moon) till we reached their hushed picket on the ridge, and bedded ourselves down beside them without words.

In the morning Auda had us afoot before four, going uphill, till at last we climbed a ridge, and plunged over, down a sand slope. Into it our camels sank knee-deep, held upright despite themselves by its clinging. They were able to make forward only by casting themselves on and down its loose face, breaking their legs out of it by their bodies’ weight. At the bottom we found ourselves in the head-courses of a valley, which trended towards the railway. Another half-hour took us to the springing of this, and we breasted the low edge of the plateau which was the watershed between Hejaz and Sirhan. Ten yards more, and we were beyond the Red Sea slope of Arabia, fairly embarked upon the mystery of its central drainage.

Seemingly it was a plain, with an illimitable view downhill to the east, where one gentle level after another slowly modulated into a distance only to be called distance because it was a softer blue, and more hazy. The rising sun flooded this falling plain with a perfect level of light, throwing up long shadows of almost imperceptible ridges, and the whole life and play of a complicated ground-system — but a transient one; for, as we looked at it, the shadows drew in towards the dawn, quivered a last moment behind their mother-banks, and went out as though at a common signal. Full morning had begun: the river of sunlight, sickeningly in the full-face of us moving creatures, poured impartially on every stone of the desert over which we had to go.

Auda struck out north-eastward, aiming for a little saddle which joined the low ridge of Ugula to a lofty hill on the divide, to our left or north about three miles away. We crossed the saddle after four miles, and found beneath our feet little shallow runnels of water-courses in the ground. Auda pointed to them, saying that they ran to Nebk in Sirhan, and that we would follow their swelling bed northward and eastward to the Howeitat in their sum............