Hence Fresnel's hypothesis as to the behaviour of ether inside matter is equivalent to the assumption that a potential function, ∫ μ² v cos θ ds , exists throughout all transparent space, so far as motion of ether alone is concerned.

Given that condition, no first-order interference effect due to drift can be obtained from stationary matter by sending rays round any kind of closed contour; nor can the path of a ray be altered by etherial drift through any stationary matter. Hence filling a telescope tube with water cannot modify the observed amount of stellar aberration.

The equation to a ray in transparent matter moving with velocity u in a direction φ, and subject to an independent ether drift of speed v in direction θ, is

ds / (V/μ cos ε + v/μ² cos θ + u[1 − (1/μ²)] cos φ) = const.

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Science for the General Reader

WORLDS IN THE MAKING

The Evolution of the Universe. Svante Arrhenius, of the Nobel Institute, Stockholm. Illustrated. 6s. net

Explains the origin of nebulæ from suns and suns from nebulæ, the universal distribution of life, the conservation of energy, etc., and shows how all may be accounted for by the newly developed principle of the pressure of light

ASTRONOMY WITH THE NAKED EYE