Sound can be produced by a multitude of things. In 1829 Arthur Trevelyan demonstrated with a similar model to the English Royal Society, that also metals that are cooling down can produce a clear tone. A wedge-shaped piece of metal (copper, brass, iron or zinc) is attached to a long brass bar of which the other end can be clamped on a wooden baseboard. The bar is attached in such a way that the piece of metal is barely supported by a lead block . When this is done after heating of the metal end, the lead will expand and give to the bar a little push upwards. Gravity makes the bar fall back upon the lead, after which the process is repeated. The vibration created in this way produces an audible tone.