The Rev. J. W. MacGaule/s Reply to Dr. Ritchie. 131 



he speaks of a magneto-electric machine^ an apparatus long in 

 use, and which requires a permanent magnet, but no battery ; 

 I, in my paper, of an electro-galvanic helix, a species of elec- 

 trical machine which requires a battery but no permanent 

 magnet: he, of an arrangement whose expense must be consi- 

 derable, and whose power can never be great; I, of one easily 

 obtained, and of almost unlimited energy. If he maintains 

 that he has anticipated me in his inquiries on the subject, then 

 they are most unfortunate, since their results are perfectly at 

 variance with the truth. I shall quote his own words : " It 

 is a well-known fact, that we receive a more powerful shock 

 when electricity is being induced on a body, than when the 

 induced electricity is returning to its natural state." Now it 

 so happens that in the apparatus I describe in my paper, no 

 shock is obtained when the electricity is being induced^ a most 

 powerful one when it is returning to its natural state. So much 

 for Dr. Ritchie's claim to my first position. 



He tella us my second position — " The spark and shock do 

 not depend, except within certain limits, on the size of the 

 battery," — is found in Dr. Faraday's papers, " On the length 

 of the coil influencing the sparks 1 presume he arrives at this 

 conclusion by the same process of reasoning as that by which 

 he inferred my first position to be one of his discoveries. But 

 first, in treating of the spark, Dr. Faraday would not neces- 

 sarily have included the shock, since they are known to be in- 

 fluenced by very different laws; and secondly, in these cele- 

 brated papers the inquiry is about the spark from the se- 

 condar^ current, obtained not from an electro- but a permanent 

 magnet, and without the agency of a galvanic battery, which 

 my second position supposes. 



He says that in my third position I assert, that " mag- 

 netism within a helix proportionably injures its effect." He 

 quotes, indeed, words which I have used, but he gives an}'- 

 thing rather than the principle I aftirm, simply because the 

 context is suppressed. Why, if 1 take an isolated expression 

 of his, I can make his talk very egregious nonsense. The 

 assertion I do make is this, and I repeat it, — that if the iron 

 of an electro-magnet retain, from the nature of its material, 

 the presence of a keeper, or any other cause, the magnetism 

 induced upon it, the shock and spark will be proportionably 

 diminished, because the magnetism of the bar, by its induc- 

 tive action on the helix, would prevent the perfect restoration 

 to equilibrium of the electricity disturbed in the helix, by 

 giving to the bar in a greater or less degree the nature of a 

 permanent magnet, from which, by means of a helix coiled 



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