As soon as he felt the air growing chill with the coming change, Tafas got up, and two minutes later we were swinging forward again. An hour after it grew bright, as we climbed a low neck of lava drowned nearly to the top with blown sand. This joined a small flow near the shore to the main Hejaz lava-field, whose western edge ran up upon our right hand, and caused the coast road to lie where it did. The neck was stony, but brief: on each side the blue lava humped itself into low shoulders, from which, so Tafas said, it was possible to see ships sailing on the sea. Pilgrims had built cairns here by the road. Sometimes they were individual piles, of just three stones set up one above the other: sometimes they were common heaps, to which any disposed passerby might add his stone⁠—not reasonably nor with known motive, but because others did, and perhaps they knew.