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.