and thus the land is now below the level of the sea. Between Coahuila Valley and the river there are many low, ashen-gray mountains standing in short ranges. The rainfall is so little that no perennial streams are formed. When a great rain comes it washes the mountain sides and gathers on its way a deluge of sand, which it spreads over the plain below, for the streams do not carry the sediment to the sea. So the mountains are washed down and the valleys are filled. On the Arizona side of the river desert plains are interrupted by desert mountains. Far to the eastward the country rises until the Sierra Madre are reached in New Mexico, where these mountains divide the waters of the Colorado from the Rio Grande del Norte. Here in New Mexico the Gila River has its source. Some of its tributaries rise in the mountains to the south, in the territory belonging to the republic of Mexico, but the Gila gathers the greater part of its waters from a great plateau on the northeast. Its sources are everywhere in pine-clad mountains and plateaus, but all of the affluents quickly descend into the desert valley below, through which the Gila winds its way westward to the Colorado. In times of continued drought the bed of the Gila is dry, but the region is subject to great and violent storms, and floods roll down from the heights with marvelous precipitation, carrying devastation on their way. Where the Colorado River forms the boundary between California and Arizona it cuts through a number of volcanic rocks by black, yawning canyons. Between these canyons the river has a low but rather narrow flood plain, with cottonwood groves scattered here and there, and a chaparral of mesquite bearing beans and thorns. Four hundred miles above its mouth and more than two hundred miles above the Gila, the Colorado has a second tributary--"Bill Williams' River" it is called by excessive courtesy. It is but a muddy creek. Two hundred miles above this the Rio Virgen joins the Colorado. This river heads in the Markagunt Plateau and the Pine Valley Mountains of Utah. Its sources are 7,000 or 8,000 feet above the sea, but from the beautiful course of the upper region it soon drops into a great sandy valley below and becomes a river of flowing sand. At ordinary stages it is very wide but very shallow, rippling over the quicksands in tawny waves. On its way it cuts through the Beaver Mountains by a weird canyon. On either side grease-wood plains stretch far away, interrupted here and there by bad-land hills. 21 powell-canyons-4.jpg SAN FRANCISCO PEAK. 22 CANYONS OF THE COLORADO.