When the Southern Pacific engineers undertook to avert the peril that menaced the Imperial Valley in the summer of 1906, they found little in recorded history to help or guide them. Inundations, of course, had often occurred before, on the Mississippi River and its tributaries, in the valley of “China’s Sorrow,” and in many other parts of the world; but these floods were merely overflows on a relatively flat surface. The cosmical plunge of a great river into the dried-up basin of an ancient sea was an unprecedented phenomenon, and one which raised engineering problems that were wholly new. Nobody had ever before tried to control a rush of 360,000,000 cubic feet of water per hour, down a four-hundred-foot slope of easily eroded silt, into a basin big enough to hold Long Island Sound. There was nothing in the past experience of the world that could suggest a practicable method of dealing with such conditions. Neither was much help to be obtained from the advice of hydraulic experts. Of the forty or fifty eminent engineers who visited the Colorado delta in 1905 and 1906, hardly any two agreed upon a definite plan of defensive work, while almost everyone found something objectionable in the measures suggested by others. All admitted, however, that “the situation was a desperate one;” that it was “without engineering parallel;” and that “there seemed to be only a fighting chance of controlling the river.” Mr. Harriman, who believed and who once said that “nothing is impossible,” never doubted that the control of the Colorado River was within human power and human resources. In building the Lucin cut-off across the Great Salt Lake of Utah he had successfully carried through one “impossible” enterprise, and he did not hesitate to undertake another. Inspired by his invincible courage, President Randolph and his engineers set about their herculean task.