The sound irritated Jack, sleepless as he was.
"It sounds for all the world as if there was a big buzz saw or a threshing machine at work," he mused. "Where on earth does the racket come from?"
He lay awake listening for a few moments longer. Then he got out of bed and tiptoed across the room where Bill lay snoring violently.
The lad looked out of the window. The street and a public square lay far below him. Only a few lights shone on the thoroughfare. It appeared deserted but for the sentries marching up and down unceasingly.
"Nothing there," said the boy to himself. "I guess I'll turn in again."
The buzzing sound had grown fainter now. It was hardly audible in fact. But for some reason it lingered in Jack's mind. It was like half a dozen things he could think of and yet he could not recall ever having heard that precise sound before.
At last he dozed off, and then sank into a dream in which it seemed to him that he was somewhere far out in the country lying under a shady tree contentedly chewing on a bit of grass and gazing up through the leafy branches at the bright sky. But suddenly everything clouded over. The landscape grew dark and sinister, and the leaves of the tree above him began to toss and sway in a harsh wind.
In his dream, Jack arose and standing up looked about him. It appeared to him as if he was gazing down from a height over an immense battlefield. He could see the dust and smoke as cannon were wheeled into position and then the flashes of flame and the belching of fire from the rifle pits. Men were mowed down like ripe grain in long windrows.
Then, all at once, came again that strange buzzing sound. But now it seemed to have in it a menacing note. It was like a terrible voice. The boy shuddered as he heard it, harsh and inexorable, filling the air, which seemed to vibrate to the steady humming.
It grew sharper and louder. Above all, the noise of the dream cannon and rifles, the boy could hear it. He awakened with a start, his heart beating rather wildly.
"That was a kind of a nightmare," he said to himself. "Glad I woke up. I guess--what's that?"
Again that humming sound filled the air as if a pulsing chord, strung at high tension, had been twanged.
"It's outside!" exclaimed Jack, for the second time going to the window.