is
significant from the instrumentation point of view that the frog's legs
were unquestionably by far the most sensitive detector of metal-contact
electrical effects available at the time. Without their intervention the
development of this entire subject-area, including the creation of
chemical cells, might have been delayed many years. Volta himself
realized that the crucial test between his theory and that of Galvani
required confirming the existence of metal-contact electricity by some
electrical but nonphysiological detector. He performed this test
successfully with an electroscope, using the "condensing" technique he
had invented more than a decade earlier.

Instrumenting Voltaic or Galvanic Electricity, 1800-1820

In his famous letter of March 20, 1800, written in French from Como,
Italy, to the president of the Royal Society in London, Volta made the
first public announcement of both his "pile" (the first English
translator used the word "column"), and his "crown of cups" (the same
translator used "chain of cups" for Volta's "couronne de tasses"). The
former consisted of a vertical pile of circular disks, in which the
sequence copper-zinc-pasteboard, was repeated 10 or 20 or even as many
as 60 times, the pasteboard being moistened with salt water. The "crown
of cups" could be most conveniently made with drinking glasses, said
Volta, with separated inch-square plates of copper and zinc in salt
water in each glass, the copper sheet in one glass being joined by some
intermediate conductor and soldered joints to the zinc in the next
glass.

Volta considered the "crown of cups" and the "pile" to be essentially
identical, and as evidences of the electrical nature of the latter,
said:

... if it contains about 20 of these stories or couples of metal, it
will be capable not only of emitting signs of electricity by
Cavallo's electrometer, assisted by a condenser, beyond 10 deg. or
15 deg., and of charging this condenser by mere contact so as to make
it emit a spark, etc., but of giving to the fingers with which its
extremities (the bottom and top of the column) have been touched
several small shocks, more or less frequent, according as the
touching has been repeated. Each of these shocks has a perfect
resemblance to that slight shock experienced from a Leyden flask
weakly charged, or a battery still more weakly charged, or a torpedo
in an exceedingly languishing sta