Along the Potomac
Potomac = Civil War
The Potomac River was the border between Union and Confederate territory. This is a Civil War poem about a soldier's death.
Geometric death
Dickinson uses surveying language—bullets 'clipt an angle' so he could 'pass quickly round' the corner from life to death. War makes dying mathematical.
Pride in heaven?
Christian theology says pride is a sin, even in Paradise. But can a mother not be proud of her dead soldier son? Dickinson questions the doctrine.
Permanent vision
They don't rest in peace—they 'pass back and forth' like stars in orbit, forever moving through her mind.