  It is shown that Maxwell's equations in media without source can be written
as a contact Hamiltonian vector field restricted to a Legendre submanifold,
where this submanifold is in a fiber space of a bundle and is generated by
either electromagnetic energy functional or co-energy functional. Then, it
turns out that Legendre duality for this system gives the induction oriented
formulation of Maxwell's equations and field intensity oriented one. Also,
information geometry of the Maxwell fields is introduced and discussed.
