Zenas C. Robbins to Abraham Lincoln, 13 April 18491
My Dear Sir.
It affords me much pleasure to inform you that I have obtained a favorable decision on your application for a patent for your improved manner of combining expansible buoys with a vessel, and operating the same.2 The patent will be issued in about a month.
Wishing you prosperity and happiness, I remain
Truly yoursZ. C. RobbinsHon A. Lincoln
1Zenas C. Robbins wrote and signed this letter.
2The idea for an invention began germinating in Abraham Lincoln’s mind while traveling abroad the steamboat Globe from Washington, DC to Springfield, Illinois, after the first session of the Thirtieth Congress. Lincoln and his party came upon another steamer, the Canada, which had become stranded on a sandbar on Fighting Island. Lincoln watched as the Canada’s captain employed empty casks and other materials to buoy up the vessel and free it from the obstruction. Lincoln began to envision an apparatus that would lift boats over sandbars and shoals, allowing for easier passage in shallow waters. Lincoln’s idea was to attach something akin to a bellows on each side of the hull of a vessel which, together with a system of ropes and pulleys, would lift the boat and move it clear of any obstacle. Upon returning to Springfield, Lincoln composed a description of his device and secured the assistance of Walter Davis, a mechanic who operated a shop near the Lincoln & Herndon Law Office, to construct a model of the apparatus. Lincoln took the miniature with him when he returned to Washington in November 1848 for the second session of the Thirtieth Congress. He hired Washington attorney Zenas C. Robbins to help him secure a patent. On March 10, 1849, Abraham Lincoln submitted his patent application and a model of his invention to Commissioner of Patents Edmund Burke. On May 22, the U.S. Patent Office approved Lincoln’s application and issued him patent number 6,469.
Jason Emerson, Lincoln the Inventor (Carbondale: Southern Illinois University Press, 2009), 4-6, 18.

Autograph Letter Signed, 1 page(s), Abraham Lincoln Papers, Library of Congress (Washington, DC).