HANS CHRISTIAN OERSTED 215 



by his own discovery.^ What may diminish the credit due for 

 a discovery is - apart from want of understanding of its im- 

 portance, which was by no means the case with Oersted - 

 mainly the circumstance of its having resulted from ap- 

 pliances previously created by others, appliances which to a 

 certain extent already contained the discovery hidden in them, 

 and only needed to be used in a somewhat different way, in 

 order that the discovery might be brought to light. For this 

 reason, we must place Galvani and Volta alongside Oersted. 

 All the same, it took no less than twenty years before Volta's 

 battery caused a magnetic needle to move before eyes which 

 could understand the matter. 



Immediately after the first observation, Oersted obtained, 

 with the help of some of his learned friends, a larger 'galvanic 

 apparatus,' consisting of twenty voltaic elements, each a large 

 copper trough filled with dilute acid and with a zinc plate 

 dipping into it, in order to make a further study of the 

 effect under as favourable conditions as possible. ^ He 

 determined in detail the changes in direction of the mag- 

 netic needle with different positions and directions of the 

 conductor, above it, below it, sideways, and at different dis- 

 tances; the result was the discovery of all that we can state 

 even to-day, without going into the matter quantitatively. 

 He saw clearly that the newly discovered force emanating 

 from the conductor was not an attraction or repulsion of the 

 magnetic poles, but that it is directed in circles around the 

 conductor. Conductors of eight different metals were tried, 

 and found practically equal in effect, but the path of the 

 current must not be interrupted, say by too long a layer of 

 water. The effect is operative through glass, metal, wood, 



1 For example, Davy of course knew very well that he was looking for 

 metals in the caustic alkalis, but the peculiar properties of the metals 

 potassium and sodium which he found were no less new and surprising 

 to him than to everyone else. See also Nature, Aug. 29, 1931. Article 

 by Kirstine Meyer, 'Faraday and Oersted.' 



2 He later announced that so many elements are not necessary, a fact 

 obvious to us to-day froin Ohm's law. 



