It is quite unnecessary to dwell on a number of further verifications of Lorentz’s theory. All that we have wished to show is that the empirical discoveries that lend weight to Lorentz’s electronic theory are so numerous that it can certainly not be cast aside lightly. Although no achievement in theoretical physics can ever claim to be permanent, yet in view of the wonderful accuracy of Lorentz’s previsions it would require some reason of a truly imperative nature [Pg 132] for us to feel justified in tampering with it in any essential detail. Lorentz’s electronic theory is also perfectly consistent with the negative experiments we have heretofore mentioned, since it explains the existence of the Fresnel convection coefficient; and we have seen that this coefficient in turn accounts for the negative results of experiments conducted to the first order of approximation in dielectric media moving through the ether. But Lorentz’s theory as it now stands suggests that experiments conducted to a higher order of precision, to the second order, for example, would cease to yield negative results; so that with experiments of this sort our motion through the ether would be detectible.[43] Now, the Michelson and Morley experiment is precisely of this type. It is a second-order experiment. It is assumed that the reader is sufficiently familiar with it to render its detailed description unnecessary. Stated briefly, the experiment proves that if waves of light leave the centre of a sphere simultaneously, they will return in perfect unison to the centre of the sphere after having been reflected against the sphere’s inner surface, no matter in what direction through the ether, or with what constant velocity, the sphere attached to the earth may be moving. An explanation was suggested by both FitzGerald and Lorentz, and was to the effect that the sphere had contracted in a definite degree in the direction of its motion through the ether. The sphere accordingly became an ellipsoid, and Michelson’s negative result was explained. More generally, any body, a yardstick, for example, when lying in the direction of the earth’s motion through the ether, would be contracted and become shorter than when placed perpendicularly to the ether hurricane. However, we should never have any means of detecting this contraction, for all things, the human body included, would participate with it, whence observationally, at least, nothing would be changed.