I believe that an early 1800 should still be positive ground, is that how you have it hooked up?  If this is correct, I believe that to polarize the generator, you hook a wire to which ever side of the battery that you wish to be hot, (Negative for a positive ground system), and touch the other end of the wire to the field post on the generator.  Just touch it a couple of times.  That is all there is to it.  Has been a while since I did this, but it is pretty simple.  Hope this helps, Terry.