Every scientific subject probably conceals unexplored or little
investigated strata, which may show up at the proper time when
favourable conditions coincide (practical demands, a circle of
scientists prepared to recognize the novelty and capable of giving
impetus to the development of a new theory, etc.). Something like this
occurred in early seventies for magnetohydrodynamics, which at the time
was considered to be a relatively complete branch of hydro- dynamics
with no apparent broad, unexplored areas. It was unexpectedly realized
that, in addition to the traditional methods of affecting an
electrically conducting medium, there is yet another way, one which
subsequently lead to a new direction in magnetohydrodynamics. In the
Soviet scientific literature this direction has been termed
'electrically induced vortex flows', the essence of which are
hydrodynamic effects due to the interaction of an electric current
passing through the fluid with its own magnetic field. It cannot be said
that this direction was created ex nihilo: individual studies related to
the flows driven in a current-carrying medium in the absence of external
magnetic fields appeared in the sixties; in the thirties the flows them-
selves were known to take place within electrical arcs; and yet the
first observa- tions on the behaviour of liquid current-carrying
conductors were made at the beginning of this century.