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in a way that they are affected by the Lorentz transformation according to equations (4) and found the ordinary law of gravitation, whenever the velocities $\xi ,\eta ,\zeta ,\xi _{1},\eta _{1},\zeta _{1}$ are small enough that one can neglect the squares in respect to the square of the speed of light.

The answer must be affirmative. It is found that the corrected attraction consists of two forces, one parallel to the vector $x,y,z$, the other to the velocity $\xi ,\eta ,\zeta$.

The difference to the ordinary law of gravitation, as I have said, is of order $\xi ^{2}$; if we only assume, as Laplace did, that the speed of propagation is that of light, this discrepancy is of order $\xi$, that is to say 10.000 times larger. It is therefore, at first sight, not absurd to assume that astronomical observations are not precise enough to detect a difference as small as the one which we imagine. But this is what only a thorough discussion will make possible to decide.