and on Thin Plates. 



37 



1. The bands form simultaneously, or nearly so. 



2,^ Plates of grease, water, vapour, go through all the 

 thicknesses without colours; but as soon as friction forms 

 vapour, or the finger approximates the atoms, colours appear. 



3. By holding the bottle to the fire, or even by the heat 

 of the hand, circular currents of red, white, blue, rise in a 

 green field; and, at all times, coloured atoms are both as- 

 cending and descending, contrary to gravity and thickness, 

 the bands increase in breadth as they descend. 



4-. To end. I have succeeded in making a film sufficiently 

 thick, with soap, as to counteract cohesive attraction, yet suf- 

 ficiently thin to evaporate without undergoing any change of 

 colour. 



The following diagrams give the different stages of the 

 atomic theory of colours. 



Fig. 1. 



green. 



Fig. 2. 



Fig. 3. 



black. 



white. 



all black. 



In fig. 2, how can different thicknesses produce three- 

 fourths of the film white ? In fig. 3 there is a very small 

 segment of white at the bottom, and by shaking the bottle 

 the entire film becomes white, and then forms into chromatic 

 bands. The best method of seeing these minute saponaceous 

 atoms forming colours, is to shake fig. 2, when atoms no 

 larger than the point of a pin are diffused in the black, and 

 after a time are seemingly dissolved in the black atoms, just 

 as when a lump of white sugar is dissolved in hot water; 

 at first the solution is clouded, and then the saccharine atoms 



