An account of /he Electro- Magnetic Engine. 119 



which a wire is coiled, and a pair of proportionably large plates of 

 zinc and copper, connected together by a wire, and separated by an 

 acid diluted with water, to be able to produce magnets capable of 

 bearing several hundred weight ; and also of depriving the most pow- 

 erful magnets in an instant of their magnetic virtue, or of completely 

 reversing their poles. This peculiarity of being able to produce mag- 

 nets of almost unlimited power, and of again instantaneously reversing 

 their power of attraction and repulsion, led very naturally to the idea 

 of employing these forces as a moving power, as steam or water has 

 been hitherto used. 



It being, however, necessary for the judicious and practical applica- 

 tion of the electro-magnetic powers, to be acquainted with the general 

 laws which govern them, we shall take the liberty of mentioning 

 the most important of them here.* 



The various experiments of the scientific have succeeded in establish- 

 ing the following results, which we shall record with as much brevity 

 as possible : — ■ 



I. As to the influence of the strength of the current on the intensity 

 of the magnetism produced in the iron. Fechner dal Negro and 

 Professor Jacobi have shewn by experiments, that the intensity of 

 the magnetic power produced in soft iron is proportioned to the 

 strength of the current applied. 



II. As to the influence of the thickness of the wire of thes pirals 

 employed on the magnetism produced, the experiments of Lenz and 

 others have shewn that the greater or less thickness of the coils em- 

 ployed is wholly immaterial as to their capabilities of magnetizing ; 

 but that as the thicker the wire is the greater its conducting power, 

 the thinner wires require stronger electrometers than the thicker ones, 

 in order to produce a current of equal intensity. 



III. As to the width of the coils, or the diameter of the spirals, or 

 the distance of the wire from the centre of the iron, it appeared that 

 the magnetism produced by spirals of different widths ; but, cceteri$ 

 paribus, was proportional to the strength of the current actually coming 

 into play ; and that the trifling difference arising from the greater 

 distance of the coils from the centre of the iron, which was experienced 

 in practice, may be wholly disregarded. So that it might be considered 



* The Translator begs leave to refer such of his readers as desire to become more thorough- 

 ly acquainted with the laws here alluded to, to the proceedings of a Meeting of the British 

 Association for the Advancement of Science, held at Glasgow, a correct report of which, 

 as far as relates to this interesting subject, will be found in No. 678 of the Athetucum. 



