By the time Bob Ackley crossed the Harlem River into Manhattan he’d been up for nearly four hours. It was still dark, not yet seven on a Sunday morning: the best time of the week to go sniffing for gas. The back seat of his hatchback was littered with hi-tech equipment. Plastic hoses and cables connected a web of instruments: a laser spectrometer, a computer, GPS equipment, a pump, and a fan. The jumble of gadgets purred reassuringly as he drove.