elegraph-wires--as recorded in Chapter XIX.; but the value of the
magnetic telegraph in war cannot be exaggerated, as was illustrated
by the perfect concert of action between the armies in Virginia and
Georgia during 1864. Hardly a day intervened when General Grant
did not know the exact state of facts with me, more than fifteen
hundred miles away as the wires ran. So on the field a thin
insulated wire may be run on improvised stakes or from tree to tree
for six or more miles in a couple of hours, and I have seen
operators so skillful, that by cutting the wire they would receive
a message with their tongues from a distant station. As a matter
of course, the ordinary commercial wires along the railways form
the usual telegraph-lines for an army, and these are easily
repaired and extended as the army advances, but each army and wing
should have a small party of skilled men to put up the field-wire,
and take it down when done. This is far better than the
signal-flags and torches. Our commercial telegraph-lines will
always supply for war enough skillful operators.

The value of railways is also fully recognized in war quite as much
as, if not more so than, in peace. 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. These points could usually be reached only by a
dash of the enemy's cavalry, and many of these block houses
successfully resisted serious attacks by both cavalry and
artillery. The only block-house that was actually captured on the
main was the one described near Allatoona. Our trains from
Nashville forward were operated under military rules, and ran about
ten miles