Now we shall go to the analysis of earlier works on an electrodynamics.

A. Sommerfeld writes following in [13] the head 1 § 6 page 62:

/Citation/ In Hertz's experiences and in many other optical experiences air can be treated as vacuum. Air and vacuum to distinguish necessarily only in a case especially of exact definitions of waves lengths.

We use here all time a word "vacuum" instead of another, of often used word "ether"("the light ether" , "the luminiferous ether" - note is my). We think, that such negative word, as the vacuum, nevertheless has more content, than scholastic word "ether", which one can reduce only to incorrect notion incompatible to the theory of relativity. /end of citation/

Inasmuch as the publication of this work is closer to time, when the theory of relativity was forcing out the ether theory from official science, A.Sommerfeld could not ignore the given problem. From the citation follows, that vacuum is considered by Sommerfeld more probably as a medium, than as its absence. However Sommerfeld does offer no model of vacuum in the one's work. The Sommerfeld's vacuum, as medium, has only two properties, namely dielectric and magnetic permeabilities, as well as vacuum of a modern electrodynamics. About the structure of vacuum, about its involvement in transmission of electromagnetic waves through space is informed nothing. As for the rest, the views of the modern authors correspond to Sommerfeld's views, therefore I will be not iterating, by citing the corresponding.

The work [14] is published else earlier and corresponds to glances of "the ether theory". The Author of this work is one of founders of electrodynamics - Hans Lorentz.

/Citation/ Thus the result, obtained by us is above, shows, that the possibility of perturbations propagation in a free ether follows from the Maxwell equations, which ones (perturbations - my note) are transmitted as plane waves with a velocity c. (speed of light - my note) /end of citation / chapter VI § 1 page 162.

Lorentz considers an electromagnetic wave in one's work, as the perturbation in some medium, in "ether", just so it was considered by Maxwell. This medium is the conductor of the electromagnetic perturbation, it explains the physical ability of an electromagnetic wave be propagated in space. It is explained more clearly and in detail by Maxwell (see below). Well and the Maxwell's equations are used only as a mathematical substantiation of the existence possibility of such perturbation.