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Yet, because the effect is caused by rotation, its occurrence is a necessary postulate not only from the standpoint of the aether theories, but equally well also from the anti-aether standpoint.

c) Thus this effect doesn't prove the aether.

6. The correctness of assertion a) follows without further ado, by thinking of the system as having a rectilinear uniform translation instead of the rotation process.^[1] Then the effect is missing.

I omit the prove (which is in general easily given) because a remark by Sagnac himself in an older work^[2] seems to speak for the fact, that his view doesn't contradict that of mine in this point.

Fig.3

7. Also with respect to assertion b), a schematizing sketch shall suffice:

First it is easily given: The occurrence of the effect is also then a necessary postulate, when one considers the process during the rotation, not in the way of § 4 (rotating disc thought as at rest, relative aether wind all around), but from

1. For example that one (changing continuously), which is approximately executed by point $O$ individually at every moment (in the direction of the circle tangent, the velocity is $v=2\pi \cdot N\cdot r$ as given above).
2. G. Sagnac, Congrès International de Radiologie et d’Électricité, p. 221, Brussels 1911.