MICHAEL FARADAY 255 



The magnetic lines of force were likewise first introduced 

 by Faraday in this essential significance, and in one much 

 wider in scope; they had hitherto been known only as the 

 lines in which iron filings arrange themselves around a mag- 

 netic pole. For Faraday they soon became the most essen- 

 tial feature of the magnet, as also of electric current, as pic- 

 turing the state in the space around the magnets and currents, 

 and indeed everywhere where magnetic forces are present - 

 everywhere as we say to-day, where a 'magnetic field' exists. 

 Nothing has proved of greater importance and more fruitful 

 than this conception of lines of force, as regards our con- 

 tinued progress up to to-day in this great domain of electro- 

 magnetic phenomena, opened up to us by Faraday. 



At the same time the way was also pointed out to the 

 use of induction phenomena, some decades later, as means 

 for the production of electric current on a large scale; for 

 every phenomenon, the laws of which are sufficiently well- 

 known and reduced to quantitative expression, is also ready 

 to be carried out on any scale desired. Faraday himself had 

 thus shown the way from the weak galvanometer deflections 

 which he observed to the dynamo machine of Siemens 

 thirty years later; he was the discoverer of the natural pro- 

 cesses from which modern electrical engineering derives its 

 possibilities. 



Already in January of the following year, Faraday had 

 produced further new forms of induction; 'earth induction,' 

 and 'unipolar induction.' The first, produced by the 

 cutting of the earth's magnetic lines of force by moving con- 

 ductors, became, in the hands of Wilhelm Weber, par- 

 ticularly important for the extension of our knowledge in this 

 field, up to the foundation of the electrical system of measure- 

 ment used to-day. 



Faraday then allowed these investigations to drop for a 

 time, so that the extraordinarily important discovery of 

 'self-induction' only occurred three years later. In the 



