Repulsion of a Rectilinear Electrical Current on itself. 365 



quantities in my method of solution is possible ; because they 

 are not of the nature of additional data, and their introduction 

 does not limit the problem as any hypotheses which are of that 

 nature do. I do not see any difficulty whatever in the concep- 

 tion of the ideal problem." 



We thus join issue as follows : Prof. Boole says that there is 

 no difficulty in understanding, I say that I do not understand, 

 the rationale of his solution. 



It may be remarked that the question may be, not to find any 

 actual probability whatever, but only to find a Boolian probability 

 or probabilities. Thus the equations (L), p. 356, omitting the 

 last member, which alone involves u, determine in terms of the 

 data a, /3, up, fiq the Boolian probabilities #, y, s y t of the events 

 A, B, AE, BE. 



In a subsequent hastily-written letter, Prof. Boole gives an 

 explanation of the equations (L), which appears to me little more 

 than a translation of these equations into ordinary language. 



April 16, 1862. 



LII. Remarks on Ampere's Experiment on the Repulsion of a 

 Rectilinear Electrical Current on itself. By Mr. James Croll. 



To the Editors of the Philosophical Magazine and Journal. 

 Gentlemen, 



IN the Philosophical Magazine for February last, Professor 

 van Breda of Haarlem* describes an experiment wherein, in 

 order to show that the movement of the conductor in the experi- 

 ment of Ampere is not due to the influence of angular currents, 

 he suspends the conductor above the mercury, and allows the 

 currents in the latter to pass underneath. A current which was 

 found to be more than sufficient to move the conductor when 

 floating upon the mercury, according to Ampere's experiment, 

 was made to pass through the apparatus; but not the least motion 

 in the suspended conductor could be observed, and he therefore 

 concludes that the motion of the conductor in the experiment ot 

 Ampere cannot be due to the influence of angular currents. 



It is remarkable how Prof, van Breda did not observe that a 

 motion of translation in the case of his suspended conductor was 

 absolutely impossible ; for he allows his conductor to cross the 

 currents in the mercury j and the consequence, of course, is, the 

 currents in the mercury repel the one half of his conductor and 

 attract the other half ; for instance, they attract the perpendicular 



* In a note recently received from Prof. Logeman of Haarlem, we are 

 informed that his name should have been associated with that of Prof, van 

 Breda as joint author of the communication here referred to. — Eds. 



