TRANSMISSION THROUGH METALS, ETC. 13 



On the Existence, in the Rays emitted by an 

 Auer Burner, of Radiations which tra- 

 verse metals, wood, etc. (May n, 1903). 



A focus tube emits, as I have already 

 proved (see p. 7), certain radiations sus- 

 ceptible of traversing metals, black paper, 

 wood, etc. Amongst these, there are some 

 for which the index of refraction of quartz 

 is nearly 2. On the other hand, the index 

 of quartz for the rays remaining from rock- 

 salt, discovered by Professor Rubens, is 

 2 *i 8. This similarity of indices led me 

 to think that the radiations observed in the 

 emission of a focus tube would very likely 

 be near neighbours of the rays discovered 

 by Rubens, and that, consequently, they 

 would be met with in the radiation emitted 

 by an Auer burner, which is the source of 

 such rays. I accordingly made the following 

 experiment : an Auer burner is enclosed in 

 a kind of lantern of sheet-iron, completely en- 

 closed on all sides, with the exception of open- 

 ings for the passage of air and combustion 



