Masterpieces of Science 



a battery of a single cup, a number of helices is 

 required; but when a compound battery is used, 

 then one long wire must be employed, making 

 many turns around the iron, the length of wire 

 and consequently the number of turns being 

 commensurate with the projectile power of the 

 battery. 



In describing the results of my experiments, 

 the terms intensity and quantity magnets were 

 introduced to avoid circumlocution, and were 

 intended to be used merely in a technical sense. 

 By the intensity magnet I designated a piece of 

 soft iron, so surrounded with wire that its mag- 

 netic power could be called into operation by an 

 intensity battery, and by a quantity magnet, a 

 piece of iron so surrounded by a number of sepa- 

 rate coils, that its magnetism could be fully de- 

 veloped by a quantity battery. 



I was the first to point out this connection of 

 the two kinds of the battery with the two forms 

 of the magnet, in my paper in Silliman's Journal, 

 January, 1831, and clearly to state that when 

 magnetism was to be developed by means of a 

 compound battery, one long coil was to be im- 

 ployed, and when the maximum effect was to 

 be produced by a single battery, a number of 

 single strands were to be used. 



These steps in the advance of electro-magnet- 

 ism, though small, were such as to interest and 

 astonish the scientific world. With the same 

 battery used by Mr. Sturgeon, at least a hundred 

 times more magnetism was produced than could 

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