"Now, I'll try to give you some idea of what I think is the method being used," went on the doctor, ignoring General Merton's rising color. "In the past, rain has been produced in several cases where conditions were right—that is, when the air held plenty of moisture which refused to fall—by the discharge from a plane of a cloud of positively charged dust particles. Ergo, a heavy negative charge in the air, which will absorb rather than discharge a positive charge, should tend to prevent rain from falling. I believe that a stream of negative particles is being liberated into the air near here, and allowed to drift where it will. That was my theory when I had the First Air Division equipped with those dust ejector tubes.
"I knew that if such a condition existed, the positively charged dust would be pulled down toward the source of the negative particle stream, which must, in many ways, resemble a cathode ray. That was why I wanted the behavior of the dust clouds watched and reported. What I did not foresee was that the iron and steel parts of the plane, accumulating a heavy negative charge, would be magnetized enough to slow down the motors and eventually wreck the ships."
"We have had eight ships wrecked unexplainably within twenty miles of here, all of them to the south, during the past year," said Colonel Wesley.
"It had slipped my notice. At any rate, the behavior of the ships this afternoon showed me that my theory is correct, and that some such device exists and is in active operation. Our next task is to locate it and destroy it."
"You shall have every man on the Proving Ground!" cried Colonel Wesley.
"Thank you. General Merton, will you detach three ships from the First Air Division by radio and have them report here? I want two pursuit ships and one bomber, with a rack of hundred-pound demolition bombs. All three must have duralumin cylinder blocks."
"I'll do it at once, Doctor," the general agreed.
"Thank you. Carnes, telephone Washington for me. Tell Dr. Burgess that I want Tracy, Fellows and Von Amburgh, with three more men down here by the next train. Also tell him to have Davis rig up a demagnetizer large enough to demagnetize the motors of a transport plane and bring it down here to fix up General Merton's ship. When you have finished that, get hold of Bolton and ask for a dozen secret service men. I want selected men with Haggerty in charge."
"All right, Doctor. Shall I tell Miss Andrews to come down as well?"