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The second class of facts to which we have alluded has reference

to the question whether or not the motion of the earth in space

can be made perceptible in terrestrial experiments. We have

already remarked in Section V that all attempts of this nature

led to a negative result. Before the theory of relativity was put

forward, it was difficult to become reconciled to this negative

result, for reasons now to be discussed. The inherited prejudices

about time and space did not allow any doubt to arise as to the

prime importance of the Galileian transformation for changing

over from one body of reference to another. Now assuming that the

Maxwell-Lorentz equations hold for a reference-body K, we then

find that they do not hold for a reference-body K′ moving

uniformly with respect to K, if we assume that the relations of

the Galileian transformation exist between the co-ordinates of K

and K′.