To my mind, the desert is the most interesting place in the world for exploration and geographical study. This is alto- gether a matter of personal taste and to that extent at least will not require an explanation. Far from being uninhabited, every desert has a great many people in it and a great many more who live just on its borders, where they are grouped in com- munities that trade with the larger citics and towns of the wet- ter regions near by and the still smaller cities and towns of the desert interior. They take great risks with the rain. Now they have years of plenty, and again they have years of drought and distress. How came a desert people to seek so severe an envi- ronment? So long as the well-watered lands will support more population, why do some go into—or remain in—the desert? There has been estimated to be many millions of people living in the deserts of the world, the Sahara alone supporting two millions within its borders. Of the fifty million square miles of land surface on the earth one fifth, or ten million square miles, are desert. It may seem sur- prising that anyone should endure the risk and distress of desert living until we remember that desert folk are not scat- tered over bare rock and lifeless sand but live grouped in oases for the most part, where their gardens look as prosper- ous as those of Connecticut or Virginia. Just as mountain people live in valleys among the mountains and not on moun- tain peaks so desert people live in the watered spots and not on the sand dunes. Though we hear much of the nomadism of the desert, there are far more desert dwellers living on farms than there are living from wide-ranging flocks and herds. And even the nomad generally winters or summers, according to the quality and time of the rains, in some home site where for a time at least he leads a more settled life.
The Desert as a Geographical Laboratory
Any land that has severe conditions of life is a geographical laboratory. If men there take risks with nature they can sur- vive only by adapting their life accordingly. Again, every des- ert scttlement tends to fill up. When a desert valley has been
