An hour that has become known for its heartbreaking declines proved a boon on Thursday, as stocks gained 400 points in the final minutes, despite a rash of weak reports on the health of the economy.

The Dow Jones industrial average, which had swung wildly throughout the day, mounted its recovery on the back on shares of energy companies and consumer favorites like McDonald’s. The index finished up 401.35 points at 8,979.26, but not before lurching more than 800 points up and down the chart.