#PreMarket Primer: Tuesday, February 25: Mt. Gox Disappears, Bitcoin Down 20%

After reaching five-year highs, natural gas retreated more than 10 percent Monday while the major U.S. markets were up sharply. Monday, the Dow gained about 104 points to close at 16,207.14. The S&P was up 0.6 percent, or about 11 points to close at 1,847.61, and the NASDAQ was down 0.7