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 promise may be seen just peeping over the crest (Fig. 19). Long, slender cloud filaments project eastward over the mar- gin of the desert. They are traveling rapidly, but they never advance far over the hot wastes, for their eastern margins are constantly undergoing evaporation. At times the top of the cloud bank rises well above the crest of the Coast Range, and it seems to the man from the temperate zone as if a great thunderstorm were rising in the west. But for all their menace of wind and rain the clouds never get beyond the desert out- posts, In the summer season the aspect changes, the heavy yellow sky of the desert displaces the murk of the coastal mountains and the bordering sea.

An early morning start in October enabled me to witness the whole series of changes between the clear night and the murky day and to pass in twelve hours from the dry desert belt through the wet belt and emerge again into the sunlit terraces at the western foot of the Coast Range. Two hours before day- light a fog descended from the hills, and the going seemed to be curiously heavy for the beasts. At daybreak my astonishment was great to find that it was due to the distinctly moist sand. We were still in the desert. There was not a sign of bush or a blade of grass. Still, the surface layer, from a half inch to an inch thick, was really wet. The fog that overhung the trail lifted just before sunrise and at the first touch of the sun melted away as swiltly as it had come. With it went the sur- face moisture, and an hour after sunrise the dust was once more rising in clouds around us.

We had no more than broken camp that morning when a merchant with a pack train passed us and shouted above the bells of the leading animals that we ought to hurry or we should get caught in the rain at the pass. My guide, who, like many of his kind, had never before been over the route he pre- tended to know, asked him in heaven's name what drink in dis- tant Camana whence he had come produced such astonishing effects as to make a man talk about rain in a parched desert. We all fell to laughing, and at our banter the stranger stopped his pack train and earnestly urged us to hurry, for, he said, the rains beyond the pass were exceptionally heavy this year. We