 Complete the following phrase:  Secretary Mellon had helped persuade the Federal Reserve Board to lower interest rates in 1921 and 1924; lower interest rates contributed to a booming economy, but they also encouraged stock market speculation. In 1928, responding to increasing fears of the dangers of speculation and a booming stock market, the Federal Reserve Board began raising interest rates. Mellon favored another interest rate increase in 1929, and in August 1929 the Federal Reserve Board raised the discount rate to six percent. The higher rate failed to curb speculation, and the activity on the stock market continued to grow. In October 1929, the New York Stock Exchange suffered the worst crash in its history in what was called 