322 Dr. Tyndall on the Progress of the Physical Sciences : 



must proceed not only along the connecting wire from pole to 

 pole, but also through the apparatus itself; that the resistance 

 offered to the passage of the current consisted therefore of two 

 portions, one exterior to the apparatus and one within it. At a 

 stroke, the difficulties which up to this time had beset the sub- 

 ject, and which were thought insuperable by those who had con- 

 fined their attention to the exterior resistance only, crumbled 

 away. 



" Ohm brought forward his discovery in the simple earnest 

 language which distinguishes the true investigator of nature. A 

 theory, he says, which lays claim to immortality must not de- 

 pend upon the idle garniture of words for the proof of its noble 

 origin, but must show in all its parts, by its simple and complete 

 correspondence with facts, and without the aid of eloquence, its 

 affinity to that spirit which animates nature. The manner in 

 which this theory was received was different in different lands. 

 Henry of Princeton, North America, who at once saw its infi- 

 nitely practical importance, observes, ' When I first read Ohm's 

 theory, a light arose within me like the sudden illumination of 

 a dark room by lightning.' The Royal Society of London 

 awarded him the Copley Medal, the highest prize given by the 

 Society for physical investigation. In France also the discovery 

 met with the greatest recognition which a foreign investigator 

 could expect there. A physicist of that country thought it con- 

 venient to rediscover the same thing years afterwards. He 

 thought, cette decouverte n'est pas Francaise, mais elle est digne 

 d'etre Francaise. But what reward did Ohm reap in Germany ? 

 While the most laborious empirical inquiries were instituted, 

 among which those of Fechner in Leipzic deserve especial men- 

 tion, to bring the theory in all possible ways to the touchstone 

 of experience, that science whose function it is to think the great 

 thoughts of the Creator over again, glanced down with divine 

 satisfaction from her Olympic throne upon these sublunary 

 occupations ; in the Berlin Jahrbiicher fur ivissenschaftliche 

 Kritik, Ohm's theory was named a web of naked fancies, which 

 can never find the semblance of support from even the most su- 

 perficial observation of facts j ' he who looks on nature,' proceeds 

 the writer, ' with an eye of reverence, must turn aside from this 

 book as the result of an incurable delusion, whose sole effort is 

 to detract from the dignity of nature.' " 



The investigations, of which we now purpose giving a review, 

 occupy themselves with the experimental verification of the entire 

 theory of Ohm. A portion of that theory has been already tested 

 by physicists of all lands and found true : this portion, which on 

 account of its superior importance is called the law of Ohm, forms, 

 however, but one link in the chain of causation which the philoso- 



