(5) As I state in the text, these rough data on the transparency of different substances will have to be completed by new experiments methodically conducted. I have since found that copper continues to transmit "N" rays emitted by a Nernst lamp, even when used in thicknesses of 65 cms.; that, similarly, glass is very transparent, etc. M. Bichat has studied the transparency of various bodies; in particular, he has ascertained that the opacity of a sheet of lead is due to the fact that it is superficially covered with oxide and carbonate. Metallic lead lets pass certain of the "N" radiations. (See C. R. t. cxxxviii. p. 548, February 29, 1904.)
(6) See the communications of May 25 and June 15, 1903.
(7) I have since found that, on the contrary, "N" rays have much shorter wave-lengths than those of light. (See my communication of January 18, 1904 (p. 53 of the present volume).)
(8) See note above (7).
(9) The phosphorescence may be intense, provided it be not at its maximum.
(10) The piece of gold must of course be also receiving the "N" rays.
(11) These researches have since been communicated to the Academy of Sciences. (See C. R. t. cxxxvii. p. 1049, December 24, 1903.)
(12) According to some experiments which I have made with an aluminium lens on rays issuing from a knife-blade, these should have very large indices. M. Charpentier has found that wet cardboard transmits these rays. These questions remain to be studied.
