cars and the heavier, immense autobuses, have elaborated and organized an ideal system for speed and safety in this unsettled region.
As we sped on we crossed numerous stone bridges, thrown over wads, or small streams. These are dried river-beds, sometimes shallow, sometimes deep, filled with round, white stones over which the water, greedily drunk by the merciless sun, had ceased to flow. However, some moisture had surely remained in porous layers of rock and soil, for at certain spots in the river-beds or just on their banks thick growths of flowering laurel and low tamarisk bushes still flourished. Farther out on the plain, like round nosegays, solitary terebinth trees followed the banks of the dried wads and patiently awaited the return of the waters that would bring down more of the tumbling cobbles and would search their way into the cooler shades of canyons, some of which dropped to a depth of over a hundred feet.
While crossing this first desert that I came upon in Africa, I made an observation which I subsequently confirmed on many occasions. Always and everywhere the North African trees, shrubs and grasses that grow in bunches are topped with a rounded crown. I hazarded the conclusion that the reason for this might be found in the fact that the winds across these deserts blow strong from all directions. There are probably those who would read into this fact the manifestation of a higher mind, that dictates for the plants such a shape as will afford to men and animals tried by the sun the greatest possible amount of shade. It is an uncontrovertible fact that, in the shadow of these rounded trees and bushes, great num-
