Who is "Black Burton" in The Call of the Wild?

"Black Burton" was the foolish man who decided to pick a
fight with John Thornton while he and Buck were in Circle City. Burton was already busy
"picking a quarrel" with a "tenderfoot" in the saloon, and Thornton decided to come to
the aid of the newcomer. Burton then took out his frustration on Thornton, hitting him
without notice and nearly knocking Thornton to the floor. In an instant, Buck, with a
"roar," flew for Burton's throat. Burton saved himself by throwing up an arm, into which
Buck sank his teeth. Buck's second attempt hit its mark, and he tore open Burton's
throat. A surgeon stopped the bleeding, and Buck was later acquitted of any crime during
a special "miner's meeting." However, his reputation soon spread throughout
Alaska.