As a young man, Lincoln took a boatload of merchandise down the Mississippi River from New Salem to New Orleans. The boat slid onto a dam and was dislodged only after heroic efforts. A few years later, while crossing the Great Lakes, Lincoln's ship ran afoul of a sandbar. These two similar experiences led him to invent a solution to the problem. The invention consists of a set of bellows attached to the hull of a ship just below the water line. When a vessel is in danger of getting stuck in shallow water, the bellows are filled with air, and the vessel, thus buoyed, floats clear of the obstacle. Although Lincoln probably never profited from his invention, he was a strong supporter of the patent system, saying that the patent system "added the fuel of interest to the fire of genius, in the discovery and production of new and useful things."