"An electroscope," explained the doctor. "That sheet of metal is really two sheets of gold-leaf, at present stuck together. If I rub a piece of hard rubber with a woolen cloth, the rod will become charged with static electricity. If I then touch the ball with it, the charge is transferred to the electroscope and causes the two sheets of gold-leaf to stand apart at an angle. Watch me."
He took a hard rubber rod and rubbed it briskly on his coat sleeve. As he touched the ball of the electroscope the sheets of gold-leaf separated and stood apart at a right angle.
"As long as the air remains non-conducting, the two bits of gold-leaf will hold that position. The air, however, is not a perfect insulator and the charge will gradually leak off. If I bring a bit of radioactive substance, for instance, pitchblende, near the electroscope, the charge will leak rapidly. Do you understand?"
"Yes, but how is that going to help us?"
"Saranoff is accomplishing his result by artificially compressing the atoms. It is inevitable that he will do it imperfectly, and some electrons will be loosened and escape. These electrons, traveling up through the earth will make the air conducting. To-morrow we will have a means of locating the borer under ground."
"Once you locate it, how will you fight it?"
"That is the problem I must work out to-night."
"Could we bury a charge of explosive and blow it up?"
