The (Daruin) Lagrangian, and energy, valid for systems of charged particles
when radiation is negligible, are derived in a new way that avoids the usu
al v/c-expansion. This shows more clearly their range of validity. Expressi
ng the energy in terms of canonical momenta gives the corresponding Hamilto
nian. When there are many particles it is intractable, but useful approxima
tions are given and general conclusions about magnetism of matter are drawn
from these. Macroscopic energy extremizing self-consistent vortex solution
s are presented which can be interpreted as corresponding to superconductiv
ity and ferromagnetism. There is a discussion of the quantum mechanics of t
he Hamiltonian for conduction electrons in a metal and a phase transition i
s predicted at low temperature.