  Postulating the existence of magnetic monopole in electromagnetism and
Heavisidian monopoles in gravitational interactions, a unified theory of
gravi-electromagnetism has been developed on generalizing the
Schwinger-Zwanziger formulation of dyon to quaternion in simple and consistent
manner. Starting with the four Lorentz like forces on different charges, we
have generalized the Schwinger-Zwanziger quantization parameters in order to
obtain the angular momentum for unified fields of dyons and gravito-dyons (i.e.
Gravi-electromagnetism). Taking the unified charge as quaternion, we have
reformulated manifestly covariant and consistent theory for the dynamics of
four charges namely electric, magnetic, gravitational and Heavisidian
associated with gravi electromagnetism.
  PACS No: 14.80 Hv.
