A cloud gathers, the rain falls, men live; the cloud disperses without rain, and men and animals die. In the deserts of southern Arabia there is no rhythm of the seasons, no rise and fall of sap, but empty wastes where only the changing temperature marks the passage of the years. It is a bitter, desiccated land which knows nothing of gentleness or ease..... No man can live this life and emerge unchanged. He will carry, however faint, the imprint of the desert, the brand which marks the nomad; and he will have within him the yearning to return, weak or insistent according to his nature. For this cruel land can cast a spell which no temperate clime can match.