There was a good natural-gas well on the dome’s southeast flank. Cullen had been studying it for months when one morning he took out his handkerchief and placed it over a gas-release valve. It showed no color. Still, on a hunch, Cullen returned every day for two weeks, and one morning he saw a faint hint of yellow on his handkerchief. Each day the color grew deeper, until Cullen saw a rich amber. It was just a hunch, but he was willing to bet the amber was a sign of oil.
