It is a nice bell. It is made mostly of copper, some tin, a little bit of lead, arsenic, zinc, silver and gold. The arsenic was meant to strengthen the alloy of copper, tin, and lead. This technique worked well for many years, until 1846. On February 23 of that year, the bell was rung for Washington's birthday. It cracked. It was never rung again. We are talking, of course, about the Liberty Bell. It was not originally called the Liberty Bell. It was just the official bell of the Pennsylvania State House in Philadelphia. It rang out for all kinds of official reasons, all the time. One of those times was on July 8, 1776. The Declaration of Independence had just been read in public for the first time. That's when the bell began to take on special significance. But it wasn't until the 1830s that a group of abolitionists decided to start calling it The Liberty Bell. It is a bell, then, that has grown in stature over the years. Looking at the bell in person at the Liberty Bell Center, Independence National Historic Park, one is reminded of that fact. Though it weighs in at 2080 pounds, it is smaller than many visitors expect it to be. No one knew it was going to have world-historical significance when it was made. The bell was cast, originally, to be simple and functional. The men of Pennsylvania had the bell made in England, one of the many ironies (beyond the giant crack) of the Liberty Bell. The Brits were known for making excellent bells. The Whitechapel Bell Foundry in London — makers of many famous bells including the bells of Big Ben — made the Liberty Bell and sent it to Philadelphia. The new bell cracked the first time it was tested. So, Philadelphians turned to local talent. Two fellows named John (John Pass and John Stow) melted down the English bell and used that metal to cast a new bell in 1753. When it was put up and rung, the people of Philadelphia hated it. Too much copper, they thought. Too much copper in a bell can make it sound dull. Too much tin, though, and the bell becomes overly brittle. So, the two Johns melted their bell down once more. The second bell sounded better, but not much. Isaac Norris, who had originally ordered the bell from England, wrote to the Whitechapel Foundry asking for an altogether new bell. When the new bell arrived, it was decided that it sounded no better than the one John Pass and John Stow had cast from the first British bell. Pass and Stow's bell was left in place, destined to ring out to great historical effect two decades later. All the complications around the making of the Liberty Bell point to an obvious fact. It is hard to make a good bell. It is an art. There is also a lot of science in the art. Complicated metallurgy is required. The bell masters of the great foundries of old were veritable alchemists in their nuanced attempts to blend just the right amount of lead, tin, gold and what-have-you. But all the science in the world never guarantees a good-sounding bell. There are too many variables and each bell is different. The shape and the blend of metals must accord with the size and density of the bell. An artfully crafted bell carries a beautiful hum, and that hum sounds like it could go on forever, long after the initial strike of the bell by the hammer. If you've ever heard a bell really hum, then you know the depth of that sound. When it gets down to what is called the 'fundamental,' the lowest frequency of the bell, the ringing can barely be heard. But the sound is still there. It can make you feel a little bit crazy since you are not sure whether you are hearing the bell or feeling it. 18th century human beings had a good ear for bells because they heard them so often. And a bell that was "off" sounded very off to their highly trained ears. The Liberty Bell, for all its historic significance, sounded "off." The ringing of the Liberty Bell was disappointing both in terms of the initial strike, which had a dullness, and the hum. Thanks to a Penn State professor of mechanical engineering (Gary Koopmann), it is now possible to hear what the Liberty Bell might have sounded like. The Liberty Bell had an E-Flat strike tone. Mp3s of both the cracked and un-cracked sounds are available here at the National Park Service website.