612 Southern Historical Society Papers.
On September 9th, Halleck telegraphed to McClellan: "It may be the enemy's object to draw off the mass of our forces and then at- tempt to attack from the Virginia side of the Potomac."
Lee' s j^,ooo tnen were on that day prepariyig to march 7iorthward from Frederick.
On the 1 2th Prebident Lincoln telegraphed McClellan: "I have advices that Jackson is crossing the Potomac at Williamsport, and probably the whole Rebel army will be drawn from Maryland." "Please do not let him get off without being hurt."
On the 13th Halleck telegraphed him : "I am of opinion that the enemy will send a small column towards Pennsylvania to draw off your forces in that direction, then suddenly move on Washingion with the forces south of the Potomac, and there he may cross over."
Jackson, McLaws and Walker were 07i that day investing Har- pers Ferry. On the 14th Halleck telegraphed: "Scouts report a large force still on the Virginia side of the Potomac ; if so, I fear you are exposing your left and rear."
Harpers Ferry surrendered at 8 A. M. on September 15th. And on September i6th, the day after the surrender of Harpers Ferry, he again telegraphed: "I think, however, you will find that the whole force of the enemy in your front has crossed the river ; I fear now more than ever that they will recross at Harpers Ferry, or below, and turn your left, thus cutting you off from Washington. This has appeared to me to be a part of their plan, and hence my anxiety on the subject. A heavy rain might prevent it."
This was the day when McClellan was feeling along Lee's front at Sharpsburg, and the day before the battle. No heavy rain ever did prevent Lee's moveme7its, or hinder Jackson, Longstreet or the Hills. Just before this point of time occurred one of those incidents which, unforeseen and astounding, change the conduct of campaigns and the fortunes of war.
Western Maryland is traversed by the Catoctin range of mountains running through Frederick county from the Potomac to Pennsyl- vania. Parallel and about eight miles northwest runs the South Mountain, the extension through Maryland of the Blue Ridge, the dividing line between Frederick and Washington counties.
From two miles and a half to three miles northwest of South Moun- tain runs the Elk Ridge from the Potomac, extending almost eight miles parallel to the South mountain.
The Valley of the Monocacy is east of the Catoctin. Between it and South Mountain is Middleton Valley, and between South Moun-
