(1) The rules applied are exceedingly various. (2) It is difficult to separate the qualitative problem of… — Henri Poincaré

(1) The rules applied are exceedingly various. (2) It is difficult to separate the qualitative problem of simultaneity from the quantitative problem of the measurement of time; no matter whether a chronometer is used, or whether account must be taken of a velocity of transmission, as... of light, because such a velocity could not be measured without measuring a time.

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