What make the mountain mans story sad?

I think this is who you are referring to:

There are many versions of John Henry's story. In almost all versions of the story, John Henry is a black man of exceptional physical gifts, a former slave,[1] possibly born in Tennessee.[3] Henry becomes the greatest "steel-driver" in the mid-nineteenth-century push to expand railroads from the east coast of the United States, across and through the mountains, to the frontier West. However, the owner of the railroad buys a steam-powered hammer to do the work of his mostly black steel-driving crew. To save his job and the jobs of his men, John Henry challenges the owner to a contest: Henry will race the steam-powered hammer. John Henry beats the machine, but exhausted, collapses and dies.

Are you asking about Twain's brother Henry, who was killed in a ship explosion, or does this question have nothing to do with the novel Roughing it?