The relative motion of the Earth and of the luminiferous ether

1', = time required £01' it to pass in the opposite direction.Further, let To = time required to perform the joul'lley if the earth were at rest.'l'hen '1'= Dt d = ~; aud T,= D v!! = ~ From these relations we Hnd d=Dv~ und d =D-,.c' 1) -'1) '. '+'1) whence T=v D and T'=v D + ; T~T,=2To-v'1) nearly, and -1' v T-T v=V"2'j'\ If now "it were possible to measure T-T, since V and '1'0 are knowp, we could find v the velocity of the earth's inotion through the ethel'.In a letter, published in "Nature" shortly after his death, Olerk Maxwell pointed out that T-T, could be calculated by measuring the velocity of light by means of the eclipses of Jupiter's satellites at pel'iods when that planet lay in <liffeI'ent directio)1s f!'Om earth j but that fOI' this pnrpose the observations of these coli pses rn nAt gl'C:1.tl'yexceerl in acclll'ac'y those