A westward-bound train was bearing me across the Mojave Desert one day in May. In a few swiftly passing hours we had made a six-thousand foot descent from the plateau with its fir and aspen-covered mountain, its cedar and pinon-clothed foot-hills, and its extensive forests of yellow pine. Crimson and yellow-flowered cactus, sage and chaparral, succeeded the pines. The cool mountains had given way to burned-out, umber-coloured hills, rock-ribbed arroyos, and seemingly endless desert; and the sun was growing hotter every minute.