The physical nature of the country is well suited for carrying out such a project on a scale far larger than that required for sewage purposes, and works thus carried out would, to a small extent, restore the old water _regime_ in this part of the continent. Before the vast surface changes produced during the last glacial period, three of the great lakes--Michigan, Huron and Superior--discharged their waters southward into the Gulf of Mexico by a broad river. The accumulation of glacial debris changed all this; the southern outlet was cut off, and a new one to the north was opened near where Detroit stands, making a channel to Lake Erie, which then became the outlet for the whole chain by way of Niagara. A very slight change in levels would serve to restore the present _regime_. Around Lake Michigan the land has been slightly raised, the summit above mean water level being only about 8 ft. Thirty miles from the south shore the lake level is again reached at a point near Lockport (see Fig. 2); the fall then becomes more marked. At Lake Joliet, 10 miles further, the fall is 77 ft.; and at La Salle, 100 miles from Chicago, the total fall reaches 146 feet. At La Salle the Illinois River is met, and this stream, after a course of 225 miles, enters the Missouri. In the whole distance the Illinois River has a fall of 29 ft. "It has a sluggish current; an oozy bed and bars, formed chiefly by tributaries, with natural depths of 2 ft. to 4 ft.; banks half way to high waters, and low bottoms, one to six miles wide, bounded by terraces, overflowed during high water from 4 ft. to 12 ft. deep, and intersected in dry seasons by lake, bayou, lagoon, and marsh, the wreck of a mighty past." The rectification of the Illinois and the construction of a large canal from La Salle to Lake Michigan are, therefore, all that is necessary to open a waterway to the Gulf of Mexico, and to make Chicago doubly a port; on the one hand, for the enormous lake traffic now existing; on the other, for the trade that would be created in both directions, northward to Lake Michigan, and southward to the Gulf.