Henry Clemens was the quiet and studious younger brother of Samuel Langhorne Clemens, better known as Mark Twain. Like Samuel, Henry belonged to the Cadets of Temperance and worked on the Hannibal Journal. After SLC left for St. Louis in 1853, Henry assisted their brother Orion on the Muscatine (Iowa) Journal and in the Ben Franklin Book and Job Office. In the spring of 1858, he became a “mud clerk” (purser’s assistant) on the steamer Pennsylvania, employment which Samuel, then a cub pilot, helped him to obtain. Henry died on 20 June 1858 from injuries suffered in the explosion of the Pennsylvania, as Mark Twain recounted in a moving letter written at the time and in Chapter 20 of Life on the Mississippi. Samuel modeled Sid Sawyer, Tom Sawyer’s well-behaved half-brother, on Henry.