Dr. Ritchie in reply to The Rev. J. W. MacGauley. 463 



shock nor spark can be obtained. Will any one deny this ex- 

 cept Dr. Ritchie? I believe not." 



Dr. Faraday's investigations have completely established 

 the fact, that it is only magnetism (or the electricity which con- 

 stitutes magnetism) in motion which can either induce electri- 

 city on a wire, or partially prevent the electricity already in- 

 duced from returning to its natural state. A permanent mag- 

 net then mthin a coil, whilst it remains as such, can have no 

 influence ^whatever in preventing the " perfect restoration to 

 equilibrium of the electricity disturbed in the helix." It is 

 quite true that a piece of soft iron, if it could be placed within 

 a helix connected with a battery, without having magnetism 

 induced on it, would partially weaken the returning electricity 

 in the coil, by the reaction of the electricity induced on it by 

 the returning current, and the more it differs from a permanent 

 magnet the more would it act in diminishing the returning 

 current. 



The concluding part of the preceding quotation contains 

 the following remark. Since neither shock nor spark can be 

 obtained from a wire coiled round a permanent magnet, there- 

 fore a permanent magnet can diminish the spark and shock 

 which the coil would of itself give when returning to its natural 

 state. If Mr. MacGauley will look at a short paper of mine in 

 this Number, he will find that both a po^werful shock and a 

 brilliant spark may be obtained from a permanent horseshoe 

 magnet having a wire coiled round it. 



Mr. MacGauley accuses me of mistaking his results because 

 he uses a galvanic helix instead of a magneto-electric machine. 

 Now if I have not always mentioned by name the galvanic helix, 

 it was simply because the electricity induced on the conductor 

 is exactly the same whether the inducing cause be a voltaic 

 battery or a magneto-electric machine. 



We have noticed in PoggendorfF's Annalen some remarks 

 bearing upon several of the controversial papers on subjects of 

 electricity and magnetism that have appeared in our last and 

 present volumes, which we feel that we ought not, in candour, 

 to omit to mention. They occur in a note appended to an 

 abstract in that Journal of the Rev. Professor Callan's paper 

 on a new voltaic battery, inserted in our last volume, p. 472. 

 M. PoggendorfF observes, after referring his readers to a paper 

 by Dr. Ritchie also in that volume, containing a statement con- 

 troverted by Prof. Callan, " the same volume of this Journal 

 [the Philosophical Magazine] contains several other papers 

 on the subject of magneto-electricity, which, as proofs of the 

 great interest taken in this branch of natural philosophy in En- 



