Buoying Vessels over Shoals

To this day, Abraham Lincoln remains the only president to get a patent—no. 6, 469, dated May 22, 1849—on one of his inventions. When he was president, Lincoln made a trip to the United States Patent Office to get another look at the scale model that had accompanied his patent application. The original drawing of his invention was rediscovered in 1997, missing the president's signature.

Smithsonian Magazine published a brief article on the president's invention back in October 2006, wondering whether Lincoln built the scale model himself, or hired someone to do it for him.

The precise source of the model of the flotation device is unclear, though there's no doubt that the ingenuity behind it was Lincoln's. Herndon wrote about Lincoln bringing the wooden boat model into the law office, "and while whittling on it would descant on its merits and the revolution it was destined to work in steamboat navigation." A Springfield mechanic, Walter Davis, was said to have helped with the model, which was just over two feet long. But Johnston thinks it's possible that the detailed miniature Lincoln submitted may have been made by a model maker in Washington who specialized in aiding inventors. "The name engraved on top of the piece is 'Abram Lincoln,'" Johnston says. "It doesn't seem likely that if Lincoln had actually made this model, he'd have misspelled his own first name." Johnston says that the answer—yet undetermined—may lie in whether the misspelled name is also engraved under the original varnish, indicating the model to be a commission.

Would it have worked? You'll have to build it and find some shoals if you want to find out. The Smithsonian article continued:

Since no one ever tried to put the invention to use, we can't know for sure if it would have led to the revolution in steamboat navigation that Lincoln predicted. But "it likely would not have been practical," says Johnston, "because you need a lot of force to get the buoyant chambers even two feet down into the water. My gut feeling is that it might have been made to work, but Lincoln's considerable talents lay elsewhere."

Above, a detail from an illustration in Popular Mechanics
magazine, October 1924: see the article here, check out the fascinating Modern
Mechanix blog here. Below, specifications for patent 6,469 (click to enlarge).