That of M.Jean Becquerel, which would attribute it to the vibration within the atom of both negative and positive electrons, also deserves notice.

A popular account of this is given in the _Athenaeum_ of 20th April 1907 .-- ED.] These laws are simple, but somewhat singular.

The radiations emitted by a gas cannot be compared to the notes to which a sonorous body gives birth, nor even to the most complicated vibrations of any elastic body.

The number of vibrations of the different rays are not the successive multiples of one and the same number, and it is not a question of a fundamental radiation and its harmonics, while--and this is an essential difference--the number of vibrations of the radiation tend towards a limit when the period diminishes infinitely instead of constantly increasing, as would be the case with the vibrations of sound.
Thus the assimilation of the luminous to the elastic vibration is not correct.

Once again we find that the ether does not behave like matter which obeys the ordinary laws of mechanics, and every theory must take full account of these curious peculiarities which experiment reveals.
Another difference, likewise very important, between the luminous and the sonorous vibrations, which also points out how little analogous can be the constitutions of the media which transmit the vibrations, appears in the phenomena of dispersion.