THE SIZE OF ATOMS. 199 



experimental arrangements giving minute solid or 

 liquid particles scattered through a transparent 

 medium, must be the direction perpendicular to 

 the plane of polarisation. 



What you are now about to see, and what I 

 tell you I have seen through the Nicol's prism, 

 is due to what I may call secondary or derived 

 waves of light diverging from very minute 

 liquid spherules, condensed in consequence of 

 the chemical decomposing influence exerted by 

 the beam of light on the matter in the tube, 

 which was all gaseous when the light was first 

 admitted. 



plane polarised light are perpendicular to the plane of polarisation, 

 since experiment shows that the plane of polarisation of the reflected 

 ray is the plane of reflection. According to this theory, if we 

 resolve the vibrations in the [horizontal] incident ray horizontally 

 and vertically, the resolved parts will correspond to the two rays, 

 polarised respectively in and perpendicularly to the plane of reflec- 

 tion, into which the incident ray may be conceived to be divided, 



and of these the former alone is capable of furnishing a ray 



reflected vertically upwards [to be seen by an eye above the line of 

 the incident ray, and looking vertically downwards]. And, in 

 fact, observation shows that, in order to quench the dispersed beam, 

 it is sufficient, instead of analysing the reflected light, to polarise 

 the incident light in a plane perpendicular to the plane of 

 reflection." 



