The Army of the Potomac is somewhere on our flank, and we shall have to deal with it." "So be it.

The Invincibles are few but ready." Harry rode rapidly back to Lee with the return message from Ewell, and found him going into camp on the eve of the last day of June.
The weather was hot and scarcely any tents were set, nearly everybody preferring the open air.

Harry delivered his message, and General Lee said to him, with his characteristic kindness: "You'd better go to sleep as soon as you can, because I shall want you to go on another errand in the morning to a place called Gettysburg." Gettysburg! Gettysburg! He had never heard the name before and it had absolutely no significance to him now.

But he saluted, withdrew, procured his blankets and joined Dalton.
"The General tells me, George, that I'm to go to Gettysburg," he said.
"What's Gettysburg, and why does he want me to go there ?" "I'm to be with you, Harry, and we're both going with a flying column, in order that we may report upon its conduct and achievements.

So I've made inquiries.