Who was Silas Phelps in the adventures of Huckleberry Finn?

Silas Phelps was the uncle of Tom Sawyer, who Huck encountered when he impersonated Tom while trying to rescue Jim from slavery. Huck had only spent a few hours with the Phelps' when Tom Sawyer showed up and pretended to be his brother Sid. Tom and Huck then spent awhile with the Phelps' creating an elaborate, yet pointless plan to rescue Jim. Under Tom's guidance, they created a much more complicated plan to rescue Jim, when they really only needed to climb through a window to rescue him.