Stocks rose in volatile trading today after the Federal Reserve chairman, Ben Bernanke, soothed investors by stating that the central bank is ready to lower interest rates to shore up the economy.

The Dow Jones industrial average initially jumped more than 130 points on Mr. Bernanke’s comments but bobbled up and down, perhaps because investors realize that it will take more than rate cuts to restore the economy’s upward momentum. Still, Mr. Bernanke’s comments appeared to reassure a market that has stumbled since the start of the year amid growing evidence that the economy is weakening.

The Fed chief said the central bank is prepared to act aggressively to rescue a weakening economy.

“We stand ready to take substantive additional action as needed to support growth and to provide adequate insurance against downside risks,” he said.

A manager of equity trading at Baird & Co., Jim Herrick, said, “We’re seeing this pop here, but I think it’s temporary.”

He added that many investors have been betting for some time that the Fed will lower rates by a half-point at their next meeting. “There’s still subprime issues. We still have concerns about earnings, and the mortgage market.”

Investors were also likely still mindful of a profit warning today from Capital One Financial Corp. and that while rate cuts can help lubricate the economy they can’t erase woes like soured debt.

And Mr. Bernanke’s comments arrived a day after Goldman Sachs rattled some investors by forecasting a recession for 2008.

The credit card issuer warned that its 2007 profit will fall short of expectations because of increased loan delinquencies and additions to its legal reserves in the fourth quarter.

In midday trading, the Dow, which had been down more than 100 points in early trading and then popped after Mr. Bernanke’s comments, rose 90.06, or 0.71%, to 12,825.37.

Broader stock indicators also rose after Mr. Bernanke’s comments. The Standard & Poor’s 500 index advanced 6.83, or 0.48%, to 1,415.96, and the Nasdaq composite index rose 11.60, or 0.47%, to 2,486.15.

Advancing issues outnumbered decliners by about 3 to 2 on the New York Stock Exchange, where volume came to 930.4 million shares.

Bond prices fell following Mr. Bernanke’s comments. The yield on the benchmark 10-year Treasury note, which moves opposite its price, rose to 3.84% from 3.83% from late yesterday. The dollar was mixed against other major currencies, while gold prices rose.