the Great Lakes, Lincoln's ship ran afoul of a sandbar. The resulting invention consists of a set of bellows attached to the hull of a ship just below the water line. On reaching a shallow place, the bellows are filled with air and the vessel, thus buoyed, is expected to float clear. The invention was never marketed, probably because the extra weight would have increased the probability of running onto sandbars more frequently. Lincoln whittled the model for his patent application with his own hands. It is on display at the Smithsonian Institution National Museum of American History. Patent #6469 for "A Device for Buoying Vessels Over Shoals" was issued May 22, 1849. In 1858 Lincoln called the introduction of patent laws one of the three most important developments "in the world's history." His words, "The patent system added the fuel of interest to the fire of genius," are inscribed over the US Commerce Department's north entrance. Courtships, marriage, and family Soon after he moved to New Salem, Lincoln met Ann Rutledge. Historians do not agree on the significance or nature of their relationship, but according to many she was his first and perhaps most passionate love. At first they were probably just close friends, but soon they had reached an understanding that they would be married as soon as Ann had completed her studies at the Female Academy in Jacksonville. Their plans were cut short in the summer of 1835, when what was probably typhoid fever hit New Salem. Ann died on August 25, 1835, and Lincoln went through a period of extreme melancholy that lasted for months. In either 1833 or 1834, Lincoln had met Mary Owens, the sister of his friend Elizabeth Abell, when she was visiting from her home in Kentucky. In 1836, in a conversation with Elizabeth, Lincoln agreed to court Mary if she ever returned to New Salem. Mary returned in November 1836, and Lincoln courted her for a time, but they had second thoughts about their relationship. On August 16, 1837, Lincoln wrote Mary a letter from Springfield suggesting an end to the relationship. She never replied and the courtship was over. In 1839 Mary Todd moved from her family's home in Lexington, Kentucky, to Springfield and the home of her eldest sister, Elizabeth Porter (née Todd) Edwards, and Elizabeth's husband, Ninian W. Edwards, son of Ninian Edwards. Mary was popular in the