Complementary Notes.
(1) As mentioned in the Preliminary Notice and as will be seen in the later communications, the properties attributed in the present paper to "X" rays, belong not to these rays, but to a new kind of rays, to which I have given the name of "N" rays. The experiments are correct, and the rectification only applies to the nature of the rays which have been studied.
(2) What I attributed then to "S" rays is, in reality, due to diffused "N" rays. The rotation of the plane of polarization of "N" rays by active substances is perhaps very great, since their wave-lengths are very small. It may be, then, that the angles I have observed are merely the remainders obtained by subtracting 360° once or several times from the real rotations. For the same reason, the rotations in a contrary direction could be apparent only. Investigation on this point remains still to be carried out; the operations should be conducted successively on each of the homogeneous pencils resulting from the dispersion of a pencil of "N" rays by an aluminium prism. The existence of magnetic rotatory polarization has recently been shown by M. H. Bagard, whose investigations are still in progress. (C. R. t. cxxxviii.)
(3) Unpolished mica arrests a pencil of "N" rays; these are not, however, absorbed, but only diffused, as in the case of light.
(4) Rock-salt is in reality transparent. What had at first misled me was that the plate of salt I used, having been sawn out of a large block, had remained unpolished. In this state it was only translucent, whether for "N" rays or for light. When polished with wet paper, it becomes transparent both for "N" rays and light; when the polish disappears, it becomes translucent again.
