As the reader knows, the Americans had no clean slate on which to write at Panama. They succeeded two French companies which had been at work for twenty years. True, the New Panama Canal Company which succeeded the Lesseps Company had not greatly perspired over the undertaking. It had kept a certain amount of work going, chiefly in order to maintain its concession. All the same, the French had ploughed a pretty deep furrow between Colon and Panama, and much of the work they had done was fortunately available whichever type of canal should be adopted, high-level or tide-level. They had carried out a good deal of dredging for the channel through the tidal flats at either end of the canal, and they had made a very visible impression on the "continental divide" at what is known as the Culebra Cut. Altogether the French companies excavated 81,548,000 cubic yards. The Americans inherited from their predecessors a large amount of machinery and tools, in addition to a great deal of work well done. Much of the machinery, even of the Lesseps Company, was found to be in serviceable condition, and operations could be continued with it, though the extent and efficiency of the plant was, of course, as time went on, greatly increased. The main problem which the American engineers had to solve was how to deal with the Chagres River. On the tide-level scheme, that violent and capricious stream, which in the rainy season was navigable for half its length of 100 miles, would have had to be diverted into another channel or ponded back in its upper waters by a high dam at Gamboa, some of the overflow of which might perhaps have been permitted to pass into the canal. But, as we have seen, the Chagres would have to be utilized and at the same time controlled if the high-level plan was adopted. A river which is capable of rising 35-1/2 feet in twenty-four hours needed a great deal of regulation and discipline before it could be used as the feeder of the upper reaches of a lock canal. The only way to do this was to diffuse its waters over a vast artificial lake which it would keep full, but in which its floods and current would be effectually tamed. This could only be done by a huge dam intercepting the course of the river in its lower reaches, at some point before it entered the Caribbean Sea. When the New Panama Canal Company changed its plans and decided for an elevated waterway, it was intended to construct such a barrier at Bohio, a point much higher up stream than Gatun, the site ultimately chosen by the American engineers. The Isthmian Canal Commission which reported in 1901, also arranged for a dam at Bohio to control the Chagres River. On this plan the river would have been intercepted much higher up, and the artificial lake would have been much smaller. But when the Americans finally decided on the high-level type in 1906, the site of the proposed dam was shifted from Bohio to Gatun, nearer the river's mouth, which involved the inundation of a much vaster