These eight gunboats, Commodore Foote ably employed in his brave attacks on Forts McHenry and Donaldson. They were the first ironclads the United States ever owned. Captain Eads covered the boats with iron: Commodore Foote covered them with glory. Eads built not less than fourteen of these gunboats. During the war, the models were exhibited by request to the German and other governments. His next work was to throw across the mighty Mississippi River, nearly half a mile wide, at St. Louis, a monstrous steel bridge, supported by three arches, the spans of two being five hundred and two feet long, and the central one five hundred and twenty feet. The huge piles were ingeniously sunk in the treacherous sand, one hundred and thirty-six feet below the flood-level to the solid rock, through ninety feet of sand. This bridge and its approaches cost eighty millions of dollars, and is used by ten or twelve railroad companies. Above the tracks is a big street with carriage-roads, street-cars, and walks for foot-passengers. The honor of building the finest bridge in the world would have satisfied most men, but not ambitious Captain Eads. He actually loved the noble river in which De Soto, its discoverer, was buried, and fully realized the vast, undeveloped resources of its rich valleys. Equally well he understood what a gigantic work in the past the river and its fifteen hundred sizable tributaries had accomplished in times of freshets, by depositing soil and sand north of the original Gulf of Mexico, forming an alluvial plain five hundred miles long, sixty miles wide, and of unknown depth, and having a delta extending out into the Gulf, sixty miles long, and as many miles wide, and probably a mile deep. And yet this heroic man, although jealously opposed for years by West Point engineers, having a sublime confidence in the laws of nature, and actuated by intense desire to benefit mankind, dared to stand on the immense sand-bars at the mouth of this defiant stream, and, making use of the jetty system, bid the river itself dig a wide, deep channel into the seas beyond, for the world's commerce. Captain Eads, who had studied the improvements on the Danube, Maas, and other European rivers, observed that all rivers flow faster in their narrow channels, and carry along in the swift water, sand, gravel, and even stones. This familiar law he applied at the South Pass of the Mississippi River, where the waters, though deep above, escaped from the banks into the Gulf, and spread sediment far and wide.