Tyndall's Apparatus

      The tag on this apparatus at the University of Vermont says that it is Tyndall's Apparatus, and the apparatus was designed to show the enormous force exerted by a bar of iron as it is cooled. Hrvoje Mesic of the University of Zagreb, who uses a similar piece of apparatus made in the early part of the 20th century in lecture demonstrations, described to me the operation of the apparatus. A gas burner composed of a long pipe with apertures in it, is slid under the square iron bar, and causes it to expand. A rod of metal about 5 mm in diameter holds the bar in place on the left-hand side and the screw on the right-hand side is tightened up as the bar expands. When the source of heat is removed, the bar cools and contracts, and eventually the rod is sheared. 

   "Tyndall" is John Tyndall (1820-1893), the Irish researcher, writer and lecturer who was the Professor of Natural Philosophy at the Royal Institution in London and later the director of the Royal Institution. His books on heat, optics and sound were widely read and admired. This apparatus may be a consequence of his studies of the effects of pressure on slate dating from the middle 1850s.

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