six o'clock in the morning
Earth passed out of sight and they were in a private world of much space and no substance , as might have been before land and sea were formed . Far below on the cloud-like surface of the fog a circular rainbow preceded them and when the operators , thinking the camp near , descending , drew near the fog , in the white center of the rainbow-circle , ghost-like , appeared a perfect silhouette of their airplane . Then through the fog , as cold as a winter mist , they came in sight of earth ; much too close for comfort , where a little dip or swerve might land them in the palm tops , and the edge of the landing field a quarter of a mile to the right , then up into the fog again and to a safe landing . On a day in July , they started for Zuara at six o'clock in the morning ; and the higher up they went the hotter it grew . The operators , returning to camp , refused to make the trip as the thermometer registered 60 centigrade at five hundred meters , stating a ghibli was raging at a higher altitude . Five hours later Tripoli and the whole desert country south , suddenly and without warning , became a blast furnace of heat and a place of dust and torture . Those familiar with the hot winds which at times devastate the crops and make life miserable southwest of the one hundredth meridian in Oklahoma and Texas would consider them the cool breeze of a summer twilight in comparison with the ghibli or Sahara sandstorm .