THEORY OF ELECTROMAGNETISM. 
779 
115. In conclusion, let me remark that in several respects the above investigations 
might be generalised. It is not bard to take account of the slipping of surfaces over 
one another, both with regard to reversible and irreversible phenomena. It is harder, 
but not impossible, to take account of the existence and relative motion in identically 
the same portion of space of two media, such as the ether and air, or as two different 
kinds of matter, as in diffusion and chemical phenomena (though, of course, in the 
two last cases, the two media do not probably really exist in the same portion of space 
—a statement not proven). I have refrained from this in the present paper for two 
reasons: first, to keep the length of the paper within reasonable bounds, and 
secondly, not to render the subject more intricate than is absolutely necessary. My 
aim has been not so much to establish incontrovertible results as to develone a new 
x 
method of treatment, more powerful, and in reality much simpler than those which 
are in use to-day. If I have succeeded in convincing my readers that this method is 
worthy of study, the main object of the present paper is attained. Meanwhile the 
matters that have been just indicated can be left over for future consideration. 
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