526 



Prof. D. E. Hughes. 



[Mar. 17, 



sitive it was to the slightest molecular change in the composition of 

 any metal or alloy, and it gave strong evidence of a peculiarity in iron 

 and steel which its magnetic properties alone failed to account for. 

 We could with all non-magnetic metals easily obtain a perfect balance 

 of force by an equivalent piece of the same metal, but in the case of 

 iron, steel, and nickel it was with extreme difficulty that I could 

 obtain a near approach to a perfect zero. Two pieces of iron cut off 

 the same bar or wire, possessing the same magnetic moment, never 

 gave identical results ; the difficulty was, that notwithstanding each 

 bar or wire could be easily made to produce the same inductive 

 reaction, the time during which this reaction took place varied in 

 each bar ; and although I could easily change its balancing power as 

 regards inductive force by a change in the mass of the metal, by heat 

 or magnetism, the zero obtained was never equal to that obtained from 

 copper or silver. 



This led me to suppose the existence of a peculiarity in magnetic 

 metals which could not be accounted for except upon the hypothesis 

 that there was a cause, then unknown, to produce the invariable effect. 



Finding that it would be impossible to arrive at the true cause 

 without some new method of investigation, which should allow me to 

 observe the effects from an electrical circuit, whose active portion should 

 be the iron wire itself, I constructed an apparatus or electro-magnetic 

 induction balance, consisting of a single coil reacting upon an iron 

 wire in its axis, and perpendicular to the coil itself ; by this means the 

 iron or other wire itself became a primary or secondary, according as 

 the current passed through the coil or wire. Now, with this appa- 

 ratus we could induce secondary currents upon the wire or coil, if the 

 coil was at any angle, except when the wire was absolutely perpen- 

 dicular ; in this state we could only obtain a current from some dis» 

 turbing cause, and the current so obtained was no longer secondary 

 but tertiary. 



The whole apparatus, however, is more complicated than .the 

 general idea given above, as it was requisite not only to produce effects 

 -but to be able to appreciate the direction of the electrical current ob- 

 tained, and have comparative measures of their value. In order to fully 

 understand the mode of experiments, as well as the results obtained, 

 I will first describe the apparatus employed. 



The electro-magnetic induction balance consists of — 1st, an instru- 

 ment for producing the new induction current; 2nd, sonometer or 

 balancing coils ; 3rd, rheotome and battery ; 4th, telephone. 



The essential portion of this new balance is that wherein a coil is 

 so arranged that a wire of iron or copper can pass freely through, 

 forming its axis. The iron or copper wire rests upon two supports 

 20 centims. apart ; at one of these the wire is firmly clamped by two 

 binding screws; the opposite end of the wire turns freely on its sup- 



