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\centerline {\bf V.M.BABICH }
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\centerline {\bf WAVES IN THE ANISOTROPIC MEDIUM }
\centerline {\bf AND ENERGETIC THEOREMS }
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In seventies of last century a young physicist N.A.Umov defended his thesis,
where an important equality was deduced. This equality with the contemporary
notation
      $$ {{\partial E}\over{\partial t}}+div{\vec S }=0, $$
here $ E $ is the density of the energy,${\vec S }$  vector of the energy
flux. The thesis contained in addition the assertion that the energy
flows in physical media as a liquid in the process of wave propagation
satisfying the classical hydrodynamical continuity equation.The conception
of the energy was not customary at that distant time.N.A.Umov ideas was not
 expressed in the rather clear form.It was naturally enough that the
standing for the degree  was violent.Dicussion continued during 3
hours...

To all appearance these ideas was expressed too early.
Only many decades later their understanding came.It was obtained,that
they are connected with asymptotic methods of mathematical theory of
wave phenomena.A hydrodynamical equation,goes back to N.A.Umov
thesis gives the possibility to integrate in explicit form so-called
transport equations of ray method.The solution has the clear
physical interpretation.

It is convenient to illustrate
\lq\lq the drama of ideas \rq\rq  an echo of which was concerned here
by the mathematical description of the process of wave propagations
in anisotropic elastic medium.

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