36 Dr. Reade on the Permanent Soap Films, 



clothed with white reflecting atoms; some of these soon 

 changed to a purple, blue, orange, &c., and when the bottle 

 was placed on an inclined plane the coloured bands were 

 formed, broad and vivid. To ascertain whether the bands 

 of colour were similar by transmission and reflection, I held 

 the film above a lighted candle, at an angle of about 4-5, and 

 perceived exactly the same coloured bands, and not any com- 

 plementary colours, " magnis componere parva." We must 

 attribute the colours of the clouds to the approximation of 

 vaporific atoms, and not to different-sized globules of water. 

 It is an interesting object of inquiry, to say why the black re- 

 flecting atoms at great distances, should by heat or agitation, 

 approximate to form white or bands of colour. We may, 

 hypothetically, surmise that these atoms are spherical, and 

 are enlarged by caloric, in the same manner as air in a bal- 

 loon or bladder ; or we may suppose that, by agitation, &c., 

 they become oblate spheroids. 



Nothing is more surprising than the permanency of this soap 

 film. In a few seconds Newton's bubble bursts, and conse- 

 quently hindered him from making deliberate observations ; 

 but now that we have one which lasts for months, can be 

 washed and renewed, an inferior mind may investigate the 

 phaenomena of light and colours with more success than even 

 that great philosopher, in the infancy of experimental science. 

 Indeed, every new experiment opens a wider field for re- 

 search, and I am sanguine enough to think that the perma- 

 nent soap film and the newly invented iriscope may produce 

 interesting discoveries. With intent to ascertain this perma- 

 nency, I formed two films with a similar saponaceous mixture, 

 in equally-sized bottles ; the one was corked, the other open, 

 and consequently exposed to the action of the atmosphere ; 

 in a short time the open one broke, the other remained 

 for weeks. I therefore inferred that the film broke from the 

 vaporific action of the atmosphere. That it was not from 

 pressure, I proved, by putting in a very long cork, so that 

 the pressure might be increased ; nor was it from agitation, 

 as supposed by Newton, for in washing the film it was well 

 shaken; neither could it proceed from any chemical action, 

 as I made the film in vacua. I remarked that a film formed 

 on the mouth of a wine glass remained a long time when 

 the atmosphere was heavy and charged with vapour, whereas 

 of a dry clay it speedily burst. I hence infer that the air in 

 a corked bottle becomes saturated with vapour, and thus that 

 evaporation is diminished. I shall now sum up the foregoing 

 arguments, to show that the colours do not proceed from re- 

 lative thicknesses. 



