The act of abolishing, or doing away with; used especially with the abolishing of slavery

Emerson uses irony to illustrate the unreasonable judgment that was made against Brown.

Irony is a rhetorical device in which what appears to be the case on the surface is radically different from what is actually the case. Emerson argues that slavery is an absurd institution because it forces the governor to hang a man who he believes to be of the most integrity, truthfulness and courage possible. The situation is ironic because you would expect a man so valued by the governor to be highly appreciated, and not condemned and killed.