shallow flow may still be found. If, leaving the railway, he crosses a river by some bridge of boats or local ferry, he will find still wider expanses of sand sometimes bare and dry and white, at others moist and dark and covered with dwarf tamarisk. He may notice that, before he
Fig. 11. Panjáb Rivers.
reaches the sand and the tamarisk scrub, he leaves by a gentle or abrupt descent the dry uplands, and passes into a lower, greener, and perhaps to his inexperienced eye more fertile seeming tract. This is the valley, often miles broad, through which the stream has moved in ever-shifting channels in the course of centuries. He