صفحة 54 من 212

In accordance with the principle of relativity we shall certainly

have to take for granted that the propagation of light always

takes place with the same velocity w with respect to the liquid,

whether the latter is in motion with reference to other bodies or

not. The velocity of light relative to the liquid and the

velocity of the latter relative to the tube are thus known, and

we require the velocity of light relative to the tube.