The severance sounded like an anchor chain snapping under a gale.
Fifty feet above their heads, through the open air-flow channel, the sky shrieked with the ear-splitting roar of an eighth-rank sky-trial thunderbolt. The final, punishing strike aimed at the last student in the breakthrough queue.
Down in the underground channel, the cut ends of the eighty-pound copper grounding cable whipped through the air like cut iron pythons. It scattered sparks across the damp stone.
A four-foot gap now separated the upper channel from the bedrock earth-sink.
*
Four hundred thousand volts of sky lightning were already dropping through the pylon above.
Without an unbroken circuit to ground, the charge had nowhere to go.
Within four-tenths of a second, the current would reach the cut end, ionize the air in the chamber, and arc into the next-door channels. That triggered a total sympathetic explosion that would turn to steam the grounding vault and electrocute every tester on the mountain.
