The Rev. Prof. Callan in reply. to Dr. Ritchie. 459 



Why, according to this, a person unacquainted with the sci- 

 ence would expect to obtain a spark from a single coil ! ' And 

 that,' he continues, ' the shock is best when the coil is long.* 

 My experiments do not bear out this assertion ; my machine 

 depends upon the thickness of the wire for the spark, and its 

 tenuity for the shock, within, of course, certain limits; and as 

 far as I have carried my investigations, with nine pounds weight 

 of steel, magnetized precisely to that degree which it will re- 

 tain under all circumstances save being made red hot, a wire y^^ 

 inch thick and 15 yards long gives a certain amount of quantity 

 effect, 20 yards of the same sized wire gives more, but 25 yards 

 less ; while, on the other hand, 700 yards of wire -^-^ of an inch 

 thick gives a certain degree of intensity, but 800 yards of the 

 same size less. With respect to his assertion that I have no 

 claim to the double armature, 1 shall not add another word, 

 confident as I am that I have already fully answered him on 

 that point, and in a way which I trust will be perfectly satis- 

 factory both to him and the public. 



" With respect to Mr. Saxton stating that my « piracy' con- 

 sisted not in manufacturing his instrument, but in suppressing 

 all mention of his name as connected with it, — I certainly 

 have not manufactured any of his instruments since my im- 

 proved machine was perfected, although I have had to alter 

 several, and I do not therefore see what right he has to expect 

 mention to be made of his name. 



" Of his last remark I cannot admit the truth, for so far 

 from having appropriated to myself Ampere's Bascule electrique, 

 in a paper of mine in Mr. Sturgeon's Annals, published a 

 month before Mr. Saxton's attack, I acknowledged the priority 

 of all similar contrivances of which I had any knowledge." 



No. ] 1, Lowther Arcade, Feb. 15, 1837. 



The Rev. N. J. Callan, Professor of Natural Philosophy in the 

 Roman Catholic College, Maynooth, in Reply to Dr. Ritchie. 

 (See Lond. and Edinb. Phil. Mag., vol. ix. p. 61.) 

 Dr. Ritchie says that the battery described by me has been 

 known for a long time. May I ask Dr. Ritchie why he has 

 not referred to some work where a description of such a bat- 

 tery is to be found ? He next says that he " had one exactly the 

 same, ... six or seven years ago. Dr. Ritchie neither describes 

 his battery nor refers to any description of it ; it is therefore 

 impossible for me to point out the difference between it and 

 the battery described by me in the Philosophical Magazine 

 for December (vol. ix. p. 4-72). With the aid of an electro- 

 magnet, and a small instrument for rapidly breaking commu- 

 nication between the battery and helix of an electro-magnet, 



3N2 



