,, CL 



& 



1 igure 8. -Completely useless arrangement of vertical 

 coil and horizontal, unmagnetized needle, presented in 

 the Edinburgh Philosophical Journal of 1821 as "Poggendorf's 

 Galvano-Magnetic Condenser." Almost every aspect of 

 Poggendorf's instrument has been incorrectly represented. 



The nearly simultaneous creation by Schweigger, 

 Poggendorf and dimming of an arrangement con- 

 sisting of a coil of wire and a compass needle provided 

 the first primitive version of a device to fill that need. 

 1 1 appears that Schweiggcr is clearly entitled to 

 credit for absolute priority in the discovery, but the 

 original sources suggest that both his understanding 

 11I the device and the subsequent researches he 

 performed with it were markedly inferior to those of 

 the other independent discoverers. In using the 

 generic label, "Schweigger's Multiplier," there have 

 been historical examples of attributing to Schweigger 

 considerably more sophistication than is justified. 

 Figure 7 shows an instrument designed by Oersted 

 in 1823. -" w hich he sa) s "differs in only minor partic- 

 ulars from that of M. Schweigger." < >n comparing 



figure 7 with figures 3, 4, or 5, the remark seems 

 overly generous. 



The history of the multiplier instruments has had 

 its fair share of erroneous reports and misleading clues. 

 A fine example is the illustration of figure 8, taken 

 from what is often quoted as the first report in English 

 on Poggendorf's ''Galvano-Magnetic Condenser." 31 

 The sketch is the editor's interpretation of a verbal 

 description given him by a visiting Danish chemist 

 who, in turn, had received the information in a letter 

 from Oersted. It incorporates, faithful to the de- 

 scription, a "spiral wire . . . established vertically," 

 with a needle "in the axis of the spiral," yet by mis- 

 understanding of the axial relations and of the ratio 

 of length to diameter for the coil, a completely mean- 

 ingless arragnement has resulted. The confusion is 

 compounded by the specifying of an unmagnetized 

 needle. 



Schweigger and Poggendorf, through their editorial 

 positions, were among the best known of all European 

 scientists for several decades. On one basis or another 

 their reputations are firmly established. Comparison 

 of the accounts of the early "multipliers," however, 

 suggests that the Reverend James Gumming, professor 

 of chemistry at the University of Cambridge, was a 

 very perceptive philosopher. This was well under- 

 stood by G. T. Bettany who wrote in the Dictionary of 

 .National Biography that Cumming's early papers 

 "though extremely unpretentious," were "landmarks 

 in electromagnetism and thermoelectricity," and 

 concluded that: "Had he been more ambitious and 

 of less uncertain health, his clearness and grasp and 

 his great aptitude for research might have carried him 

 into the front rank of discoverers." 



•'" "Account of the New Galvano-Magnetic Condenser in- 

 vented by M. Poggendorf of Berlin," Eclmlumji Philosophical 

 Journal (July 1821), vol. 5, pp. 112-113. 



ACKNOWLEDGMENTS 



I wish to thank Dr. Robert P. Multhauf. chairman of 

 the Department of Science and Technology in the Smith- 

 sonian Institution's Museum of History and Technology, 

 for encouragement in the writing of this paper and for 

 the provision of opportunity to consult the appropriate 

 sources. To Dr. W. James King of the American Insti- 

 tute of Physic, I am grateful for many provocative 

 discussions on this and related topics 



For sale by the Superintendent of Documents, U.S. Government Printing Office 

 Washington, D.C. 20402 - Price 20 cents 



