84 Galvanism, from Galvani to Ohm. 



up a great number of knives and forks in a large box, and 

 having placed the box in the corner of a large room, there 

 happen'd in July, 1731, a sudden storm of thunder, lightning, 

 etc., by which the corner of the room was damaged, the Box 

 split, and a good many knives and forks melted, the sheaths 

 being untouched. The owner emptying the box upon a Counter 

 where some Nails lay, the Persons who took up the knives, that 

 lay upon the Nails, observed that the knives took up the Nails." 



Lightning thus came to be credited with the power of 

 magnetizing steel ; and it was doubtless this which led Franklin* 

 in 1751 to attempt to magnetize a sewing-needle by means of 

 the discharge of Leyden jars. The attempt was indeed success- 

 ful ; but, as Van Marum afterwards showed, it was doubtful 

 whether the magnetism was due directly to the current. 



More experiments followed. f In 1805 Jean Nicholas Pierre 

 Hachette (b. 1769, d. 1834) and Charles Bernard Desormes 

 (b. 1777, d. 1862) attempted to determine whether an insulated 

 voltaic pile, freely suspended, is oriented by terrestrial mag- 

 netism ; bat without positive result. In 1807 Hans Christian 

 Oersted (&. 1777, d. 1851), Professor of Natural Philosophy in 

 Copenhagen, announced his intention of examining the action 

 of electricity on the magnetic needle ; but it was not for some 

 years that his hopes were realized. If one of his pupils is to be 

 believed,* he was " a man of genius, but a very unhappy experi- 

 menter ; he could not manipulate instruments. He must 

 always have an assistant, or one of his auditors who had easy 

 hands, .to arrange the experiment." 



During a course of lectures which he delivered in the winter 

 of 1819-20 on " Electricity, Galvanism, and Magnetism," the 

 idea occurred to him that the changes observed with the 

 compass-needle during a thunderstorm might give the clue to 

 the effect of which he was in search ; and this led him to think 

 that the experiment should be tried with the galvanic circuit 



* Letter vi from Franklin to Collinson. f In 1774 the Electoral Academy 



of Bavaria proposed the question, " Is there a real and physical analogy between 

 electric and magnetic forces ? " as the subject of a prize. 



1 Cf. a letter from Hansteen inserted inBence Jones' Life of Faraday y ii, p. 395. 



