te, which imitates still better the
effects of my apparatus by the series of repeated shocks which it
can continually communicate.[4]

The "effects" provided by Volta's pile and crown-of-cups are therefore
electroscope deflection, sparks, and shocks. Later in the letter, he
describes the stimulation of sight, taste, and hearing as noted earlier,
but nowhere does he mention chemical phenomena of any kind, or the
heating of a wire joining the terminals of either device. Hence, except
for the additional physiological responses, he adds nothing to the
catalog of observations on which instruments might be based. His
familiarity with the moods of the torpedo (electric eel) seems to be
intimate.

The reading of Volta's letter to the Royal Society on June 26, 1800, its
publication in the Society's _Philosophical Transactions_ (in French)
immediately thereafter, and its publication in English in the
_Philosophical Magazine_ for September 1800,[5] gave scientists
throughout Europe an easily constructed and continuously operating
electric generator with which innumerable new physical, chemical, and
physiological experiments could be made. Editor-engineer William
Nicholson read Volta's letter before its publication and, by the end of
April, he and surgeon Anthony Carlisle had built a voltaic pile.
Applying a drop of water to improve the "connection" of a wire lying on
a metal plate, they happened to notice gas bubbles forming on the wire,
and pursued the observation to the point of identifying the electrical
decomposition of water into hydrogen and oxygen.

Within two or three years innumerable electrochemical reactions had been
described, some of which, one might think, could have served as
operating principles for electrical instruments. Although the phenomena
of gas formation and metal deposition were in fact widely used as crude
indicators of the polarity and relative strength of voltaic piles and
chemical cells during the period 1800-1820 (and the gas bubbles were
made the basis of a telegraph receiver by S. T. Soemmering), the
quantitative laws of electrolysis were not worked out by Faraday until
after 1830, and not until 1834 was he satisfied that the electrolytic
decomposition of water was sufficiently well understood to be made the
basis for a useful measuring instrument. Describing his
water-electrolysis device in that year, he wrote:

The instrument offers the only _actual measurer_ [italics his] of