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LXI. Professor Kelland's Vindication of himself against the 

 Charges of the Rev. M. O'Brien. 



To the Editors of the Philosophical Magazine and Journal. 



Gentlemen, Paris, June 5, 1 842. 



f HAVE read, with extreme astonishment, the attack made 

 on me by Mr. O'Brien in your Magazine for this month. 

 My first impression was that it did not become me to reply 

 to it in any shape, but, on refleetion, it has appeared probable 

 that many persons may read it who are not intimately ac- 

 quainted with the subject, on whom the effect of silence would 

 be equivalent to the admission of the justice of the statements 

 made. I shall therefore enter into a brief explanation, with 

 a view to direct your readers to the facts, not to carry on a 

 controversy. But in commencing I am naturally induced to 

 ask, wherein have I offended Mr. O'Brien ? For it must be 

 noted by every one that Mr. O'Brien's object is not to " re- 

 ply " to my remarks, but to remove an impression which he 

 thinks I have endeavoured to create, M that he has done nothing 

 in his paper which had not been already done by myself 

 in my memoirs." Now I should be exceedingly sorry to 

 create a false impression ; and I am sure no person who reads 

 my remarks will accuse me of having done so intentionally. 

 Still had Mr. O'Brien candidly stated that such was the im- 

 pression on his mind, either in your Journal or personally 

 when I saw him in Cambridge, I would have addressed my- 

 self diligently to remove it. But Mr. O'Brien's procedure 

 leaves no room for any other course than to reply publicly to 

 his charges, and leave it to the world to judge between us. 



First, then, have I attributed to myself the " notation " em- 

 ployed, " the equations of M. Cauchy," the conclusion " that 

 transverse and normal vibrations are in general 'propagated 

 with different velocities ? " Never ; I am not chargeable with 

 such dishonesty. They are all, as far as I know, due to 

 Cauchy. Nor is there one of the conclusions of M. Cauchy 

 which I have, even by accident, called my own. I will not 

 waste words about this. M. Cauchy himself assures me that 

 I have spoken with perfect justice and propriety. 



Secondly, have I attributed to myself the conclusion " that 

 homogeneous light must in general suffer dispersion in passing 

 through a prism, and dispersion of a discontinuous nature, 

 and that this accounts for the dark lines in the spectrum ? " 

 I never heard of the conclusion. 



Thirdly, have I endeavoured to attribute to myself the con- 

 clusion " that the results obtained on the hypothesis of perfect 



