Francesco Folli's Hygrometer

These original hygrometers are now exposed in the ''Museo di Storia della Scienza'' in Florence (Via dei Giudici, 1).
Francesco Folli created two different types of hygrometer which he called ''mostra umidaria'' (in italian) agreeing with the archduke of Florence Ferdinando II.

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This hygrometer dates back to the XVII century too. A balustrade-shaped loom, finely tooled, made of brass, has two small rollers on its edges where the ends of a paper strip (now missing) are used a hygroscopic substance . In the middle of the loom, there's a decorated disk made of brass and a circular graduated scale. The hand on the dial, with a simple mechanical system, shows the variations of the length of the paper tape caused by changes in atmospheric humidity.1

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This hygrometer was conceived by Francesco Folli in the XVII century. It's a quadrangular wooden shaft with two small rollers on the border edges where the ends of a paper tape are wrapped, which acts as a hygroscopic substance. In the middle of the rod, placed on a support, there's a decorated disk made of brass and a circular graduated scale. The hand on the dial, with a simple mechanical system, shows the variations of the length of the paper tape caused by changes in atmospheric humidity.2

  • Main text by Chiara Goretti moc.liamg|79itterogaraihc#| and Chiara Palagiano ti.oiligriv|onaigalap.araihc#| photo credits to Museo Galileo Galilei (December 2017)

Bibliography

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