We started in a W. N. W. direction at 10.17 a. m., and in three minutes we were down in the level depression. The soil here was covered with gravel, and was in places white with incrustations of salt. The ground sank imperceptibly to the west, and we drove over one or two faint indications of an old beach-line.
After a twenty-three minutes' run on ground that could only just bear the small car and made very slow going — the motor-lorry would have got hopelessly stuck — we came to a mesa some 15 or 20 m high, looking astonishingly like the ruins of an old castle. It was a huge block of clay with in places quite vertical sides. The stratification was mainly horizontal, but in parts somewhat irregular. We stopped here for a little while, took some photographs and made hurried sketches. (Fig. 27) . At close quarters one observed thin white strata of gypsum in the reddish yellow deposit. These white strips were only 2 cm or less in thickness, while the reddish yellow layers were from 10 to 20 cm.
Immediately to the west of this stately monument, a mighty relic from the late tertiary period left by erosion, we found four more mesas, all small in size, and not so picturesque as the first (Fig. 28). Other erosion-remains, weathered by the storms of thousands of years, were to be seen at one or two other points.
We spent three-quarters of an hour in this impressive archipelago of gigantic clay blocks, that stood up like rocky islets out of an open sea. Proceeding west and W. S. W., we noted that the ground was not absolutely horizontal, there were long, smooth undulations, growing lighter in colour in proportion to their remoteness. In eight minutes we crossed a belt whose surface was strewn with sheets of gypsum, glittering in the sun. Small rudimentary dunes were to be seen here and there.
We stopped after a drive of 15 km. Getting out of the car, we let our eyes roam
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