The Voltaic Pile

   About 1791-2 Luigi Galvani (1737-98), a biologist and professor at the University of Bologna, noticed that frog's legs, impaled on brass hooks, contracted when the legs came in contact with an iron lattice. Unfortunately, he made the assumption that the source of the effect was in the animal tissue.

   In the last years of the 18th century Allessandro Volta (1745-1827) of the University of Pavia showed that any moist, porous material between two dissimilar metals would produce the same effect.

   In the Pile which Volta described in 1800, a disk of copper is placed at the bottom, followed by a disk of cloth soaked in brine or acidulated water, followed by a disk of zinc. More sets of copper-cloth-zinc disks is placed on top, until the pile reaches a height of about 30 cm. The positive end of the pile is the bottom copper disk, and the negative end is the top zinc disk. The three glass rods serve to confine the disks into a vertical pile.

   The voltaic pile shown on the right is at Middlebury College.

   Other VOLTAIC CELLS are illustrated on other pages. 

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