This piece of equipment dates from at least 1846. It was brought when the college moved from Davenport to Grinnell in that year.

This is an induction coil with a core made of iron wires--perhaps knitting needles. The primary circuit included the base which looks like part of rasp and an iron bar on the end of a wire. When the iron bar was dragged over the toothed base, the primary circuit was broken and remade many times quite rapidly. The rapid start and stop of the primary circuit induced a current in the secondary winding.