  In a recent Letter by Barnett [S. M. Barnett, Phys. Rev. Lett. 104, 070401
(2010)], a total-momentum model is proposed for resolution of the
Abraham-Minkowski dilemma. In this model, Abraham's and Minkowski's momentums
are, respectively, a component of the same total momentum, with the former
being the kinetic momentum and the latter the canonical momentum. In this
Comment, I would like to indicate that this physical model is not consistent
with global momentum-energy conservation law in the principle-of-relativity
frame.
