Page:Air Service Boys over the Rhine.djvu/100

90 is where the cunning of the invention comes in. The smaller missile has all the impetus given the larger one, but without its weight. In consequence it can travel through eighty miles of atmosphere, finally reaching Paris, where it explodes."

"Wonderful!" exclaimed Jack.

"And yet it is merely the adaptation of an old theory," went on the major. "We have known of the sub-calibre theory for years, but it is not practicable. So we did not try it. The cost is too great for the amount of military damage done. And this shell, as you will see, is composed of two parts, each with a separate explosive chamber, each containing, as we discovered, a different sort of explosive. In this way if one did not go off, the other would, and so set off the one that failed. It is very clever, but we shall be more clever."

"That's right!" chimed in a chorus of fellow officers.

"We'll find the gun and destroy it—or all of them if they have more than one, as they probably have," went on the major.

He showed the boys where the shell had chambers for the time fuses to work, much as in a shrapnel shell, which can be set to go off so many minutes or so many seconds after it reaches its objective point.