The Atlanta campaign would simply have been impossible without the use of the railroads from Louisville to Nashville--one hundred and eighty-five miles--from Nashville to Chattanooga--one hundred and fifty-one miles--and from Chattanooga to Atlanta--one hundred and thirty-seven miles.

Every mile of this "single track" was so delicate, that one man could in a minute have broken or moved a rail, but our trains usually carried along the tools and means to repair such a break.

We had, however, to maintain strong guards and garrisons at each important bridge or trestle--the destruction of which would have necessitated time for rebuilding.

For the protection of a bridge, one or two log block houses, two stories high, with a piece of ordnance and a small infantry guard, usually sufficed.

The block-house had a small parapet and ditch about it, and the roof was made shot proof by earth piled on.