How does Silas resolve the mystery of Marshal Farmer?

Sheriff Chalfon is not able to track down the old lawman. About the time of the trial, Silas comes across an article that lists all of Ollerenshaw's victims and helps him solve the mystery of Marshal Farmer. On the list is the name of Enoch Farmer, a U.S. marshal, killed while pursuing Ollerenshaw's gang into the woods near the Hollow Forest in April 1854. That was six years before Silas met the marshal.