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To explain the aberration of light it was assumed by Fresnel, that the aether does not share the annual motion of earth, which of course requires that our planet is completely permeable for that medium. Later, Stokes sought an explanation on the assumption that the aether is dragged by the earth and thus to each point at the earth's surface the speed of the aether is the same as that of the earth.
On these theories, I have extensively worked some years ago[1]. It appeared to me that other modes of explanation may more or less lie in the middle between those mentioned above, and therefore, as they are not so simple, deserve less attention. Of the two extreme views I thought it was necessary to reject that of Stokes, because the motion of the aether requires the existence of a velocity potential, which is incompatible with the equality between the velocities of the earth and the adjacent aether.
On the other side, it was possible to explain nearly all considered phenomena by Fresnel's theory, if we assume the "dragging coefficient" for transparent ponderable substances given by Fresnel, and whose value was recently derived by me from the electromagnetic theory of light.[2]
