Steven Brann was out Wednesday on the Gettysburg battlefield in Pennsylvania, sweeping the ground with a metal detector ahead of crews that are rehabilitating a famous part of the Civil War park. Thus far, park officials believe a Confederate cannon fired it toward Federal positions and mistakenly dropped shells on friendly Texas regiments trying to navigate the difficult terrain. Chris Gwinn, chief of interpretation at the park, said in an email that the shell will provide validation to accounts of the battle