The earliest established date in the "multiplier" record is September
16, 1820, when Schweigger read his first paper to the Natural Philosophy
Society of Halle. There seems to be no reason to doubt that this report
justifies the frequently used label "Schweigger's multiplier."
In an exuberant support of Schweigger's position, Speter[14] with no
mention of Cumming and no hint of "invention" details, shows that
Poggendorf in 1821 admitted Schweigger's priority, but suffered some
lapse of memory 40 years later when writing sections of his biographical
dictionary, leaving a distinct suggestion that the invention was his.
Further confusion for later generations resulted from some ambiguous
entries in the _Allgemeine Deutsche Biographie_ of 1888. The name
"multiplier" seems not to have originated with Schweigger himself.
Speter credits it to Meineke as "working" editor of Schweigger's
_Journal_, but Seebeck seems to have used it much earlier.[15]
Conceding priority of conception to Schweigger (Cumming has not been a
real competitor on this point) does not alter the fact that all three
seem to have reached their results independently of one another, that
the first work of each on this subject was published within a period of
five months, that there were significant differences in their
conceptions of the uses and the optimum design of their devices and that
between them they provided an adequate foundation for the subsequent
development of the galvanometer to become the primary
electrical-measuring instrument.
In the matter of publication, Schweigger, as editor of what was
popularly called Schweigger's _Journal_, had an obvious advantage, and
presented his experiments beginnings on page 1 of the first volume of
his _Journal_ for 1821, published January 1 of that year.[16] Oersted's
paper had appeared two volumes previously. He began by referring to
Oersted's discovery as "the most interesting to be presented in a
thousand years of the history of magnetism." He was, in fact, so
impressed with the epochal nature of Oersted's achievement that he
commemorated it by giving his _Journal_ a second title so that "volume
one" of the new title could begin in the year after Oersted's
publication.
Poggendorf, as a relatively junior student, had no such easy access to
publicity, but he had a staunch admirer in one of his professors, Paul
Erman at the University of Berlin. Erman added a seven-page postscript
on Poggendorf's invention to his book _Outline of the Physical Aspects
of the Electro-chemical Magnetism Discovered by Professor Oersted_,
published before April 1821,[17] with an introductory paragraph:
Herr Poggendorf, who is one of the most excellent ornaments of the
lecture room and laboratory of the University here, carried out a
very coherent and well-conceived investigation of electro-chemical
magnetism, leading step-by-step to a method of amplifying this
activity-phenomenon by means of itself.
The postscript begins by referring to the "condenser [_Kondensator_]
just brought to my attention by Herr Poggendorf" and explains that he
cannot release his treatise "without preliminary announcement of this
subject of the highest importance." (It can be inferred from the text
that the name "condenser" was chosen because of the device's enhancing
of magnetic measurements analogously to the enhancing of electric
measurements by Volta's electrostatic "condenser.")
Immediately on reading the book, Schweigger published extracts, mainly
of the postscript, with indignant comments on Erman's remissness (or
worse) in having failed to mention Schweigger's prior work.[18]
However, Erman was not alone in his unawareness, if it was that, of
Schweigger's discovery.
Rival editor Gilbert of the _Annalen der Physik_ reviewed Erman at much
greater length than Schweigger, reprinting most of the postscript with
evident enthusiasm, and stating in his preamble that the invention is
attributed to "a young physicist studying here in Berlin, Herr
Poggendorf."[19] Only in a footnote is the reader directed to another
footnote in the next article in the volume, where Gilbert finally states
that he "cannot leave unmentioned the fact that this amplifying
apparatus seems to be due to Herr Professor Schweigger." He then quotes
rather fully from Schweigger's first two papers.[16] Oersted in 1823
explained the situation thus: "The work of M. Poggendorf, having been
mentioned in a book on electromagnetism by the celebrated M. Erman
published very shortly after its discovery, became known to many
scientists before that of M. Schweigger. This is the reason for the same
apparatus carrying different names."[20]
The same confusion is well illustrated by the paper to which Gilbert
attached his confessional footnote mentioned above. Written by Professor
Raschig of Dresden, on April 3, 1821, the paper is entitled "Experiments
with the Electro-magnetic Multiplier," but the device, throughout the
paper, is repeatedly referred to in the phrase "Poggendorf's condenser,
or rather multiplier," an awkward combination that suggests editorial
intervention.[21]
The work of James Cumming at Cambridge is described in two papers which
he read to the Cambridge Philosophical Society in 1821, which were then
duly published in the _Transactions_ of that Society. The first, "On the
Connexion of Galvanism and Magnetism," was read April 2, 1821,[22] and
the second, "On the Application of Magnetism as a Measure of
Electricity," was read a few weeks later on May 21st.[23]
Though he quotes some unrelated 18th-century experiments by Ritter in
Germany, an 1807 publication of Oersted's, and electromagnetic
experiments with solenoids performed by Arago and Ampère in late 1820,
Cumming makes no mention of Schweigger or Poggendorf, and never uses the
word "multiplier." It, therefore, seems probable that his work was done
without knowledge of the German publications or inventions.