Davis's manual of magnetism : including galvanism, magnetism, electro-magnetism, electro-dynamics, magneto-electricity, and thermo-electricity (1854)
Davis, Daniel · Boston : Palmer and Hall · leaf 313
conve-niently illustrated by the separable helices, in con-sequence of the facility with which the powers anduses of its several parts can be exhibited. Theobservations which have been made with regard toit apply equally well to the following instrument,which is a modified form. 486. Separable… … addition to the steel rasp. There are two cups, Aand D, for the battery wires; these are connected,through the electrotome, with the inner helix. Whenthe electrotome is set in motion, the curved wiredips its ends alternately into the glass cups contain-ing mercury, and rapidly breaks the circuit.…
