  In this paper we report multifrequency single pulse polarization observations
of the PSR B0329+54 normal mode using the Giant Meterwave Radio Telescope at
325 and 610 MHz and the Effelsberg Observatory at 2695 MHz. Our observations
show that towards the central part of the polarization position-angle traverse
there is an unusual ``arc''-like structure, which is comprised of a broadband
``kink'' and a frequency-dependent ``spot.'' The features are intimately
connected with the intensity dependence of the core component: the stronger
emission arrives earlier and its linear polarization is displaced farther along
the ``kink''. Moreover, at high intensities, the circular polarization is --/+
antisymmetric; the nearly complete positive circular is characteristic of the
weaker, later core subpulses. We find that the ``kink'' emission is associated
with the extraordinary (X) propagation mode, and hence propagation effects do
not appear capable of producing the core component's broadband,
intensity-dependent emission. Rather, the overall evidence points to a largely
geometric interpretation in which the ``kink'' provides a rare glimpse of the
accelerating cascade or height-dependent amplifier responsible for the core
radiation.
