Tuesday, May 31, 1859: The Great Clock (aka Big Ben) in London officially began keeping time. (On July 11, the Great Bell first struck the hour.) The 315-foot-high tower, part of the Houses of Parliament building, has no elevator; there are 334 steps to the belfry. The four quarter bells, or chimes, ring out every 15 minutes. The Great Bell tolls every hour. The minute hand measures almost 14 feet long. The clock mechanism weighs 5.6 tons, and is wound three times a week. The clock’s time is adjusted by changing the number of old pennies sitting on a shelf near the top of the pendulum. The tune played each hour is from the aria “I Know That My Redeemer Liveth,” part of Handel’s Messiah..