192 Mr. J. Parker on the Theory of Magnetism and 



of the constancy of /uu during a cycle be denied me, and if I 



must assume the possibility of its being wrong, still p — 



must be more nearly constant than //,; for it is equal to 

 2Ly. And if \x increases and therefore L increases, y will 

 certainly diminish, and if L diminishes y will certainly 

 increase. 



XXVII. The Theory of Magnetism and the Absurdity of 

 Diamagnetic Polarity. By J. Pakker, M. A, Felloio of 

 St. Johns College, Cambridge *. 



THE most unsatisfactory part of the theory of magnetism 

 is that which refers to the so-called diamagnetic 

 bodies. This part of the theory is so beset with absurdities 

 and contradictions that it is necessary to examine it closely 

 and to point out the true explanation of the behaviour of 

 the so-called diamagnetic bodies before we can give the 

 general theory. 



I published a short and somewhat premature paper on dia- 

 magnetism in the Philosophical Magazine for May 1889. 

 A few weeks afterwards my ideas on the subject had ripened 

 into t.heir present form ; but I determined to publish no more 

 about it until after the appearance of my book on l Elemen- 

 tary Thermodynamics/ which I was then intending to write. 

 Finding, however, that my book was not likely to be finished 

 as soon as I had expected, I published a second short paper 

 on diamagnetism in the Philosophical Magazine for July 

 1890, which I thought would be sufficient to explain my 

 ideas until I could give the subject the attention it deserved. 



My second paper on diamagnetism was criticised, as I have 

 since found, by Dr. Lodge with a great display of rhetoric 

 in the next number of the Philosophical Magazine ; but I 

 was then so occupied that I did not see or hear of the criticism 

 until the following November. When I then came to read 

 it, I did not find anything which required me to, modify any 

 of my ideas on the subject in the slightest degree, and I 

 concluded that Dr. Lodge had misunderstood my paper. 



It is now proposed to consider the subject carefully and 

 completely, by which means, it is hoped, the disputed points 

 will be settled to the satisfaction of everybody. In so doing, 

 I shall endeavour to prevent all misconception by making 

 my arguments as clear and simple as possible. For this 

 reason I shall employ none but the simplest mathematics, 



* Communicated bv the Author. 



