It is necessary to pay attention to some peculiarities of experiments in Colorado. These experiments produced round scientific technical branch that is the high frequency electrophysics and they are  interesting as a basis for designing and using for high-frequency high-voltage exciters (HHE). Check up some principal qualities of his experiments:

                                     operational frequency - 160 kHz
                                     generative power - 250 kW
                                     operational voltage - 10 x 106 V
                                     fixed voltage - 100 x 106 V

 Now after 100 years these figures get in surprise. But if we make analyze for the facts more deeply, we'll see that there are no any wonders here and  N.Tesla  was real designer-scientist who could use all achievements of science and techniques for his time. Just a combination of these quantities: a genius designer and a brilliant scientist - allowed him to reach these outstanding results.

 Tesla's tank in a sparking generator electric circuit was about 3 m diameter and 5 m high (D=3 m; h=5 m). Then the first stage had factor of merit (Q) more that 103. A low frequency transformator (60 Hz) with voltage about 3 kV was a feed source for arc discharges. Tesla used combined circuit and by means of second step resonance he increased voltage up to 10 x 10 6 V. He used a ferrous mast as a capacitor of the second step circuit that allow to provide surely such sort operational voltage. The mast was 60 m high (h=60 m) and it was loaded on a cooper sphere of 1 m diameter (D=1 m).

 Telsa explained the second resonance with an assistance of stationary waves, which the transmitter exited. He considered that stationary waves go round the Earth and come back to the point of radiation so voltage of antenna is increasing; such explanation is doubtful because waves propagate for a long distance and that why they can't comeback without damp.

 It can be proposed another explanation of the second resonance. Suppose the second resonance is provided of the sphere electro-resilient properties. The sphere can resound and parametrically pump up the power. Consider feature of on adjustment (agreement) of the electro-resilient parametrical resonance. When a sphere has a high voltage, some force   F=1/8   acts on its sides. This force strives to increase the diameter of the sphere. The electroresilient properties of a hollow cooper sphere provide the parametrical resonance with double-frequency [2].

 N.Tesla fixed the second resonance in a few minutes. It means that the parametrical resonance has high factor of merit (Q 106 ). Only crystals (quartz) have such resonance. The main difficulty to reach this resonance is the adjustment (agreement), because these properties can be displayed when an oscillation energy comes through a high-reactive resistor. The ferrous mast was this adjustment (agreement) element. It had the magnetic permeability and considerable inductive resistance that made it  in some original throttle. When its magnetic permeability m is about 104, its inductance L is about 1 Hn.

 N.Tesla created an artificial lightning when he made his experiments. Its rumbles were heard at a distance of 16 miles.

 The author of this paper created a high-frequency arc in his laboratory  ( 1986 ) and this arc branched and closed on to environment (Fig.1a,b,c,d). On the Fig.2 the single discharge is shown between a couple of capacitors: one of them is a sphere and other is a toroid.

 Solution for a problem for high-voltage potential creation allow to produce the wireless energy transmission for a long distance. N.Tesla designed and began to construct a HHE of electric field (Fig.3) but unfortunately this idea was not realized to all over the end. In 1992 the author of this paper tried to carry out this idea also (Fig.4) but it was wrecked, because the woods are surrounding the exiter absorbed its radiation. Results were unstable, because electric conditions of trees depends on a season (winter-summer) and on a weather (dry - wet). In some cases trees spontaneously flared up. But idea of wireless energy transmission has the practical sense in the individual cases.

 On the basis of this idea it was made an experiment for determination of a signal transmission velocity by the vector of the electric density (D). The experiment consist in the following. HHE that includes step up transformer by patent N 2033651 creates quasi static electric field that has intensity about 0.4 x 106 V. The signal was received at two points: A=50 m and B=400 m on the frequency 135 kHz. Supporting signal was transmitted by glass fiber (fiberoptic line), and a phase shift was measured to determine the signal transmission velocity. In both cases the length of the glass fiber remained a constant. Then fixed velocity was more than velocity of  light on 16%.

 Sure, it's necessary to develop and to repeat this experiment because "purely" electric component and electromagnetic component that is determined by vertical current in HHE are transmitted simultaneously.

 There is a new theory for matter  of free space, it is theory which the N.Tesla's experiments bring for us. This theory was proposed by authors L. Gutenmacher, P.Krasnooshkin and V. Kessenikh [3]. By this theory the electric (e ) and magnetic (m) permeabilities change on corresponding specific capacity (Cs) and the specific inductivity (Ls). Then an equation for the velocity of light is

Such sort interpretation can explain many physical phenomenons of macrocosm and in particular it can explain the change of light velocity. For example, the velocity of light changes near the Earth surface because specific capacity C near the surface is increasing and then the velocity of light is decreasing.