In the south he saw a long curving line of rising blue plumes.

It did not need Colonel Newcomb to tell him that these were the campfires of the army that they had met on the field of Bull Run, and that the Southern troops were now cooking their suppers.
No doubt his cousin Harry was there and perhaps others whom he knew.
The fires seemed to Dick a defiance to the Union.

Well, in view of their victory, the defiance was justified, and those fires might come nearer yet.

Dick, catching the tone of older men who shared his views, had not believed at first that the rebellion would last long, but his opinion was changing fast, and the talk of wise Sergeant Whitley was helping much in that change.
While he yet looked through the glasses he saw a plume of white smoke coming swiftly towards the Southern fires.

Then he remembered the two lines of railroad that met on the battlefield, giving it its other name, Manassas Junction, and he knew that the smoke came from an engine pulling cars loaded with supplies for their foes.
He whispered of the train as he handed the glasses back to Colonel Newcomb, and then the colonel and the generals alike made a long examination.
"Beauregard will certainly have an abundance of supplies," said one of the generals.