I am looking for a classical book on Maxwells equation. Let me explain: For potential theory I found "Foundations of Potential Theory from Oliver Dimon Kellog from 1929. It is basically a mathematical book on electrostatics. Slow, detailed, and existence proof are about 'normal' function (not distributions, of course). I found this, because somebody mentioned this area is called 'potential-theory'

I am now looking for something similiar on either (time dependent) Maxwell-Equations or wave-equations. Of course the modern term would be partial differential equations; but I am looking for a classical text about uniqueness/existence proof all in the real of 'classical' mathematics,so pre 1950.

I am sure there must have been good books on that topic, since physics has been a driving force for mathematics, but I dont seem to be able to find them.

Edit: What I might be looking for is a classical (pre-Distribution) text on hyperbolic differential equations. Although not too sure if this is the right term (finding the term 'Potential theory' took quite some time)