‘Proof of a foregone conclusion’ is indeed the verdict at which one arrives in respect of all the observations concerned with the velocity of light – whether of existing phenomena detectable in the sky or of terrestrial phenomena produced artificially – if one studies them with the attitude of mind represented by the child in Hans Andersen’s story. In view of the seriousness of the matter it will not be out of place if we discuss them here as briefly as possible, one by one.²