He watched in growing perplexity.  The cloud moved very swiftly.  Thin as it seemed to be, it should have been silvery from the moonlight, but the sky was noticeably darker where it moved.  It advanced toward the tower and seemed to obscure the upper portion.  A confused motion became visible among its parts.  Wisps of it whirled away from the brilliantly lighted tower, and then returned swiftly toward it.

Arthur heard a faint tinkle, then a musical scraping, which became louder.  A faint scream sounded, then another.  The tinkle developed into the sound made by breaking glass, and the scraping sound became that of the broken fragments as they rubbed against the sides of the tower in their fall.

The scream came again.  It was the frightened cry of a woman.  A soft body struck the earth not ten feet from where Arthur stood, then another, and another.

XI.

Arthur urged the elevator boy to greater speed.  They were speeding up the shaft as rapidly as possible, but it was not fast enough.  When they at last reached the height at which the excitement seemed to be centered, the car was stopped with a jerk and Arthur dashed down the hall.

Half a dozen frightened stenographers stood there, huddled together.

“What’s the matter?” Arthur demanded.  Men were running, from the other floors to see what the trouble was.

“The—­the windows broke, and—­and something flew in at us!” one of them gasped.  There was a crash inside the nearest office and the women screamed again.

Arthur drew a revolver from his pocket and advanced to the door.  He quickly threw it open, entered, and closed it behind him.  Those left out in the hall waited tensely.

There was no sound.  The women began to look even more frightened.  The men shuffled their feet uneasily, and looked uncomfortably at one another.  Van Deventer appeared on the scene, puffing a little from his haste.

The door opened again and Arthur came out.  He was carrying something in his hands.  He had put his revolver aside and looked somewhat foolish but very much delighted.

“The food question is settled,” he said happily.  “Look!”

He held out the object he carried.  It was a bird, apparently a pigeon of some sort.  It seemed to have been stunned, but as Arthur held it out it stirred, then struggled, and in a moment was flapping wildly in an attempt to escape.

“It’s a wood-pigeon,” said Arthur.  “They must fly after dark sometimes.  A big flock of them ran afoul of the tower and were dazed by the lights.  They’ve broken a lot of windows, I dare say, but a great many of them ran into the stonework and were stunned.  I was outside the tower, and when I came in they were dropping to the ground by hundreds.  I didn’t know what they were then, but if we wait twenty minutes or so I think we can go out and gather up our supper and breakfast and several other meals, all at once.”