NEW SPECIES OF LIGHT 



On a New Species of Light (March 23, 1903). 



The radiations emitted by a focus tube are 

 filtered through a sheet of aluminium foil or a 

 screen of black paper, in order to eliminate the 

 luminous rays which might accompany them. 

 While studying these radiations by means -of 

 their action on a small spark, I discovered that 

 they are plane-polarized as soon as emitted. I 

 further proved that when these radiations tra- 

 verse a plate of quartz in a direction at right 

 angles to its axis, or a lump of sugar, their 

 plane of action undergoes a rotation just like 

 the plane of polarization of a pencil of light 

 (see pp. 5 and 6). 



I then asked myself if a rotation could also 

 be obtained by passing the radiations of the focus 

 tube through a pile of Reusch mica sheets. I 

 observed, in fact, a rotation of from 25 to 30 in 

 the same direction as that of polarized light. 

 This action of a pile of micas made me at once 

 infer that a single sheet of mica must act, and 

 that this action must be depolarization, or, rather, 

 the production of elliptic polarization ; this is 



