Magnetic field and its physical nature

The article consists of two parts. The first part (F. Mende) presents the field theory of field transformation in classical electrodynamics. He constructed a notation that used the discovered derivative that Maxwell used when writing his membership. in this form Maxwell''s equations are invariant to Galilean transformation. In the second part (A. Kukushkin and A. Rukhadze) a critical review of approaches to describing the energy of electromagnetic fields is given as well as a review of theoretical and experimental work on the frequency of waves from the point of view of the special theory of relativity ( ONE HUNDRED). The equations of motion for an energetic wave in vacuum are formulated and a simple exact equation for the 3-vector energy velocity is obtained.