Velocities of the Spiral Nebulæ.

THE extraordinary velocities of recession which are derived from the shift toward the red of the spectral lines of remote galaxies have led to much scepticism of the interpretation of this shift as a Doppler effect; and this scepticism is enhanced when it is learned that the velocities are proportional to the distances of the galaxies. No other interpretation in terms of ether waves seems to be satisfactory, but there is an interpretation in terms of light quanta, or photons, that is much less disturbing.