WHAT IS ELECTRICITY? 



By Paul R. Heyl 

 National Bureau of Standards 



I trust that there is no one so optimistic as to suppose that because 

 I have asked this question I am going to answer it, nor so pessimistic 

 as to fear that because I have asked a question which I cannot answer 

 I can offer you nothing but platitudes. I believe it possible in this 

 case to avoid both Scylla and Charybdis. 



This question, said the late Prof. John Trowbridge,^ of Harvard 

 University, is often asked as though it were capable of a short and 

 lucid answer which might be understood by any person of liberal 

 education. Many answers have been given, but it is interesting to 

 note that the more definite and confident the answer the older it is, 

 and that as we ascend the ladder of time toward the present day such 

 answers as we encounter are less definite and more cautious. 



It will be interesting to review, perhaps rather briefly, the ideas 

 which have been held at various times as to the nature of electricity, 

 and then, looking over the wealth of physical discovery which has 

 been amassed in the past 40 years, to endeavor to select from it such 

 facts as may be of importance in guiding and controlling future 

 speculation on this question ; for though such speculation has been at 

 a minimum, if not a standstill, during the twentieth century, it will 

 doubtless revive again. Speculation, or, as it has been otherwise 

 termed, " apt conjecture, followed by careful verification ", has been 

 behind much of the advance of science. Such was the method of 

 Faraday and of Darwin. The conjectures of the ancients, having lit- 

 tle in the way of observed fact to guide them, might range far and 

 wide, and had small heuristic value, but with the growth of experi- 

 ment the range of conjecture has continually narrowed and its value 

 as an aid to further progress has steadily increased. 



The beginning of our Imowledge of electricity is lost in the mists 

 of antiquity. What we can recover of it is excellently told by Park 



1 Publication approved by the Director of the National Bureau of Standards of the 

 United States Department of Commerce. Reprinted by permission from Journal of the 

 Washington Academy of Sciences, vol. 25, no. 5, May 15, 1935. 



' This is the fifth of the Joseph Henry Lectures of the Philosophical Society presented 

 March 30, 1935, in honor of the first president of the Philosophical Society. 



'Trowbridge, What is electricity? Kegan Paul, Trenoh, Trubner & Co., London, 1897. 



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