But instead of making a detour, as I momentarily expected, he held his course straight for the largest dune. It grew larger as we drew near until it loomed above us like the Equitable Building. Still we kept on at steadily increasing speed. The man must have gone daft, I thought. We had at the wheel a lunatic. For anything on wheels to attempt that towering wall of sand was as crazy a performance, it seemed to me, as Don Quixote’s encounter with the windmill. We charged it like a tank attacking the Hindenburg Line. The lower slopes we took with a rush and a roar; then came a perceptible slackening of speed as we lost momentum. With a clash of gears the chauffeur went into second speed, then third ... fourth ... fifth. The exhaust barked like a machine-gun. The big car reared itself up until it seemed to be standing on its stern. I felt the seat tilting under me, as one does when an airplane goes into a steep climb. We went into sixth speed. The staccato crackle of the exhaust changed into a sustained roar. The sandy slopes slipped by us slower and slower—ten ... eight ... six miles an hour. Would we make it? Would the power hold out? By way of answering my unvoiced question the chauffeur jammed his foot hard upon the throttle, the car flung itself forward in a final surge of power—and we were at the top. My sensation of relief died half born, however, for, though we were on the summit of the ridge, our front wheels rested upon the brink of a sandy precipice which seemed to drop away a hundred fathoms sheer. If the ascent of the windward slope had seemed perilous, the descent of this all but perpendicular leeward slope would, I felt certain, inevitably end in disaster. Yet to back down the declivity we had just ascended with so much effort was out of the question, while the space at the top was too narrow to permit of turning around. But our pilot showed no signs of perturbation. Nonchalantly lighting a cigarette, he shifted into lowest gear and gently nosed the cumbersome machine over the brink. The little flags out front, then the hood, seemed suddenly to drop out of sight, and I was thrown forward with great abruptness to find myself looking down upon the top of the driver’s head. Do you know the sensation of diving in an airplane? Well, it was like that, only more so. I would have sworn that no wheeled vehicle ever built could have descended that declivity and remained right side up at the bottom. But this one did. Indeed, it seemed entirely to defy the law of gravitation. If the ascent had been exciting, the descent was paralyzing. We went down with a rush and a roar, choked and blinded by the whirling sand, at a speed so terrific that it literally took the breath away. I gripped the sides of the seat until my fingers ached. You can see their imprints sunk in the steel arms to-day! Half-way down the driver shut off his power, and from there on we coasted. I glanced at the speedometer. The needle showed 130 kilometers an hour!