Mr. Swift, Blake, Voorhees, and Dr. Faber were on hand for the test, as well as numerous plant employees. They watched in silence as Tom climbed into the remote-control booth.
Trying to remain calm, Tom snapped on the main switch, then started feeding power into the machine.
At first there was a smooth, steady whine as the blaster plowed downward into the earth. But a moment later came a thunderous, ear-shattering roar like a thousand pneumatic hammers ripping into
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concrete! Under the impact, the control booth and the surrounding ground began to vibrate and shudder!
Quickly Tom shut off the blaster and climbed out of the booth to find out what was wrong.
“Well, what now?” inquired Voorhees smugly. “Another contact bomb?”
Bud gave him a withering look.
Tom consulted with his father.
“I believe we’d better remove the blaster and examine the shaft,” the elder inventor suggested.
Tom donned a safety suit and climbed down into the shaft to make the examination. When he returned to the surface and pulled off his plastic headgear, he was smiling.
“Did you find the cause?” Mr. Swift asked.
“There’s a shelf of basaltic bedrock down there we never knew about. The rock transmits vibrations in all directions. No wonder we got shaken up when the blaster bit into it!”
The earth blaster was now replaced in position, and boring resumed until the shaft was three or four yards deeper. Although the vibration continued, there was no doubt that the blaster itself was operating perfectly!