PRELIMINARY NOTICE
The present volume contains the memoirs on the subject of "N" rays, communicated to the Academy of Sciences by Prof. R. Blondlot. The papers have been reprinted exactly as they were originally published in the Comptes Rendus of the Academy. The notes at the end were added later, with the object of throwing light on certain points which were obscure at the time the papers were communicated to the Academy.
The title of the first memoir in this collection, "On the Polarization of 'X' Rays," will hardly cause astonishment when it is realized that the study of the "X" rays led the author to recognize the existence of radiations of a totally different character. To these he gave the name of "N" rays. Before the distinction of these two kinds of radiation was made,
