"What's the matter?"
"Something's happened to these little beasts." Davis held out the test tube. "Twenty minutes ago this was full of the silver stuff. I put it down on the sounding board here and now they're smashed up and dead!"
Gerrod looked at the tube intently.
"Where was it?"
Davis showed him. Gerrod put one hand on the spot and struck a chord tentatively. His expression changed from weariness to hope.
"Wait a minute!" he exclaimed, and darted into the laboratory, to return a moment later with half a dozen test tubes full of the sticky animalcules. "We'll put another one there and strike a chord."
He did so. The contents of the test tube remained unchanged. He struck another. Still no change. Then, deliberately striking one key after the other, with the eyes of all four of them fixed hopefully on the test tube, he began to go up the keyboard. Note after note was struck, but just as they were about to give up hopes of finding the cause of the first tube's clearing Gerrod struck a key—the F above high C. The instant the shrill note sounded out the test tube clouded—and was clear! It had lain upon the sounding board of the piano. The vibrations of the piano string had been communicated to it through the sounding board.
"Done!" shouted Davis at the top of his voice.
Nita was speechless.
"Sympathetic vibrations," said Gerrod happily. "If you could hang up one of those microscopic shells and ring it it would ring that note. So, when the vibrations from the piano strike them, they vibrate in sympathy, only the piano vibrations are so strong and the shells so fragile that they rack themselves to bits, and the animals are killed. Whee! Hurray! Hurray!"