1 6 PRESSURE OF LIGHT 



We may perhaps present Clerk Maxwell's ideas' 

 in the following way. If we rub a stick of sealing- 

 wax with flannel it becomes negatively electrified. 

 If we hold it near a conducting body such as the 

 disc in fig. I, it induces positive electrification on 

 the surface of the conductor, and the wax and the 



FIG. 4. 



conductor tend to draw together. We have every 

 reason to suppose that the air or medium between 

 the two surfaces, electrified respectively positively 

 and negatively, is modified. Perhaps the atoms 

 join hands and form atomic chains stretching from 

 surface to surface, and these chains tend to shorten 

 and so pull the surfaces together. But whatever 



