62 Smtfltrrn Historical Society Papers.
Federal army, having crossed the Potomac, was advancing north- ward, and that the head of the column had reached the South Mountain. As our communications with the Potomac were menaced, it was resolved to prevent his further progress in that direction by cencentrating our army on the east side of the mountains. Accord- ingly, Longstreet and Hill were directed to proceed from Chambers- burg to Gettysburg, to which point General Ewell was also instructed to march from Carlisle."
THE ADVANCE ARRESTED.
Again, in his later and more carefully considered report, after the reports from all the different parts of the army had been received by him, he writes (p. 316): "The advance upon Harrisburg was arrested by intelligence received from a scout on the night of the 28th, to the effect, that the army of General Hooker had crossed the Potomac, and was approaching the South Mountain. In the absence of the cavalry it was impossible to ascertain his intentions; but to deter him from advancing further west and intercepting our communications with Virginia, it was determined to concentrate the army east of the mountains."
Acting under the impression produced by the scout's information, that the Union army was moving westward towards Hagerstown, on the line of his communications with Virginia, it must have been a great surprise to him, when his leading divisions approached Gettys- burg, to find Meade's advance was there ahead of him.
It had evidently been General Lee's plan to operate west of the South Mountain range, and keep General Meade east of it, as the sending Early east of it to threaten Baltimore clearly indicates. In case the Union army crossed over in spite of his manoeuvres to pre- vent it, he relied upon the fact that the concentration of his army at Gettysburg would place him nearer to Baltimore than it, and unless his move was quickly responded to by it, he could interpose his army between Baltimore and Washington on the one side and the Union army on the other. He was in error in supposing that con- tingency had arisen, though it appears from the fact on the morning of the 28th, three of the seven corps of the Union army were in the Catoctin Valley, near Middleton, and one other at Knoxville, with the passes in the South Mountain heavily guarded, that it was Hooker's purpose to have crossed over as General Lee supposed he was doing.