The Photographic History of The Civil War: in ten volumes, Thousands of Scenes Photographed 1861-65, with Text by many Special Authorities, Volume 2: Two Years of Grim War.
Francis Trevelyan Miller, Ed.

Mute pleaders in the cause of peace

There was little time that could be employed by either side in caring for those who fell upon the fields of the almost uninterrupted fighting at Gettysburg. On the morning of the 4th, when Lee began to abandon his position on Seminary Ridge, opposite the Federal right, both sides sent forth ambulance and burial details to remove the wounded and bury the dead in the torrential rain then falling. Under cover of the hazy atmosphere, Lee was getting his whole army in motion to retreat. Many an unfinished shallow grave, like the one above, had to be left by the Confederates. In this lower picture some men of the Twenty-fourth Michigan infantry are lying dead on the field of battle. This regiment--one of the units of the Iron Brigade — left seven distinct rows of dead as it fell back from battle-line to battle-line, on the first day. Three-fourths of its members were struck down.

Confederate dead after Gettysburg.

Dead of the Twenty-fourth Michigan Infantry, the iron brigade, after Gettysburg.