"I'll show you. Here's an instrument that measures the resistance of a given coil. This is one of the professor's evaporation machines for producing low temperatures quickly. He evaporates ether in this sheath that surrounds this oven and objects in the oven are cooled far below freezing point. Look at this coil of silver wire. We measure the resistance at room temperature. One hundred and twenty ohms. It is very fine wire. We put it in the cooling oven and set the engines going----" For some minutes there was silence while the small electric pump thumped and rattled. "Now we'll take the coil out. The thermometer inside the oven says twelve below zero." Teddy handled the small coil of silver wire with thick gloves. "We'll measure the resistance again. Fourteen and a half ohms resistance, approximately. Low temperatures decrease resistance and increase the conductivity of metals. You see?" "Yes, but why----" "The inside of that bracelet is nine hundred degrees below zero. The whole thing is coated with Varrhus' lacquer, which, in this case, radiates all the heat from the inside out, leaving it incredibly cold within. That cold makes the silver conduct electricity better." "Well?" "At eight hundred degrees below zero Fahrenheit silver has no measurable resistance to the passage of an electric current. Now watch." Teddy laid the bracelet on top of a frame wound with many turns of glistening copper wire. He threw on a switch, and a small generator at one side of the laboratory began to run with a humming purr. "Eddy currents are whirling all around that bracelet. A strong current is running in an endless circle in that closed circuit of silver, nine hundred degrees below zero. Silver at that temperature offers no resistance to an electric current. Closed circuits have been left at that degree of cold for over four hours, and at the end of that time the electric current was still flowing round and round like a squirrel in a cage." Teddy picked up the bracelet with a pair of wooden tongs. He took a second pair in his other hand. Rubber handles insulated the tongs from their handles. "There's a current flowing around the inside of this bracelet. There was one flowing around it when the professor received it in the mail. He opened it with his bare hands, suspecting nothing. I open it with these insulated tongs. Watch." He jerked on the two tongs. The bracelet parted at the catch, and a dazzling, blinding flash of light appeared with a sharp crackle at the parting. "I made the current jump the gap. The professor took it through his body and it killed him. Are you satisfied?" "God!" said the commissioner of police, aghast. "The box and wrapper," said one of the men who had come with the commissioner. "Let us have the box and wrapper the bracelet came in and we'll get the man that mailed it. But we'll handle him with tongs, too, when we close in on him." They took what they wanted and left. Teddy turned to the commandant.