when he would turn to the North — a conjecture which proved true, as in a few hours we struck again into the great Wady el Arish. After miles of weary march, we saw before us another wall of mountains, which we did not cross, but kept in view as we moved along the bed of the "River of Egypt."
Our course to-day led over great flint-covered plains. It was indeed "a dry and thirsty land where no water is," and yet all round us shone crystal lakes, only they were always out of reach, and had we advanced towards them we might have gone on forever. It was our first sight of the mirage. Observing it closely, it seemed as if it were a phenomenon very easy of explanation; that it was caused by the vibration of the heated air near the surface of the desert, which produced an illusion like that from the reflection of the sun on rippling water. Studied merely as a wonder of nature, as we study the rainbow, it was a beautiful object, but what a mocking fiend it must be to those whom it lures on and on, only to perish at last. To one dying of thirst there could hardly be a more cruel torture than this gleam of water in the distance.
Towards evening we came near mountains which, to the eye of the Doctor, resembled those of Palestine. Thus almost every day something looms up on the horizon which reminds one or the other of mountain scenery or coast scenery which is familiar. The desert, while it is like the sea in its vast expanse, is different in this, that it is a sea with the coast always in sight. I do not remember ever having been "out of sight of land." There is always at least a range of low hills on the horizon, which sometimes rise to mountains, and recall mountains that we have seen in other parts of the world. Often we seem to be sailing along a rugged coast, and can easily imagine ourselves off the west coast of Ireland, or sailing up St.
