The Twelfth corps is camping close to us. The different
corps are fortifying their positions.

_Saturday, July 11._--Marched four miles. Passed through Tillmington. The
enemy was found in front. Our columns formed in line of battle.
Skirmishing was kept up briskly. The rebels fell back a little, as our
artillery opened on them. The cavalry advanced in a body at half-past four
o'clock, gaining some ground. At midnight, the infantry was ordered to
advance and take possession of the Hagerstown road. We remained all night.
We have marched two hundred and twenty-three miles since the fourteenth of
June.

_Sunday, July 12._--We advanced a short distance at eight o'clock A. M.
Our infantry is half a mile ahead. Skirmishing was going on all the
morning. Artillery is used once in a while. All the artillery of the Fifth
corps passed by between four and six o'clock P. M. A heavy shower this
afternoon. In the evening, we changed our position, advancing a quarter of
a mile nearer to the front.

_Monday, July 13._--Changed position in the morning, going a short
distance behind breastworks. Three fortified lines are already formed by
our army. A battle is expected. We remained in our new position all day.
It rained the whole evening and night.

_Tuesday, July 14._--Advance and reconnoissance of parts of the Second,
Fifth and Twelfth corps, cavalry ahead. Our battery marched on the
Williamsport turnpike. Cannonading and musketry fire could be heard at
mid-day. The roads are very muddy. Rebel caissons, full of ammunition, are
frequently found on the roadside. Lee's army is crossing the Potomac at
Falling Waters. General Kilpatrick charged through Williamsport, capturing
the rear guard, consisting of eight hundred men. On our approach, a short
but desperate fight was going on at one of the redoubts, close to the
river. A brigade, in command of General Pettigrew, defending the redoubt,
hoisted the white flag. Forty men of the Eighth Michigan cavalry,
charging, in good faith of their surrender, were all slaughtered after
going in the trap. The redoubt was carried by the infantry shortly after;
but General Pettigrew and most of his men escaped. We had a heavy shower
this evening.

_Wednesday, July 15._--The greater part of the army is marching towards
Sharpsburg. Our battery returned to its former position. We were told to
rest until one o'clock P. M., as we had to do some marching yet. About
three o'clock we started, passed through Sh