Page:Elektrische und Optische Erscheinungen (Lorentz) 100.jpg

 repeated by and , on the propagation of light in streaming water. The arrangement of them should be sufficiently known, so that we can restrict ourselves to compare (still more deeply than it is usually happening) the results with the theory.

To apply the formula, we first have to derive the relative period from the experimental conditions, and then (from the dispersion formula for stationary water) the refraction exponent N corresponding with this period. The value of V/N calculated in this way, we eventually have to substitute into (82) for W. However, as regards the relative period, a more closer consideration is required.

It's known that, as regards these experiment, two tubes were used which are closed by glass plates and which are lying next to one another, through which the water was flowing with the same velocity, but in different direction; since the base tubes were present entirely at the edges, we may assume, that at all places (at least in the middle parts of the bisection) the same velocity $$\mathfrak{p}$$ occurred. The two light bundles, which should mutually interfere, passed through the device, so that one was propagated in both tubes in the direction of the water stream, and the other one steadily in the opposite direction.

We now consider a fixed point P in the interior of one of the tubes. The conditions, under which the light is propagating from the source to this point, obviously remain — when the water stream is stationary — constantly the same, and namely this applies to both ways, on which the rays can reach point P. Impulses, which emanate by certain periods from the source, will arrive with the same periods in P, and when T is