OF THE GASEOUS AND LIQUID STATES. 415 



Bosscha in tobacco smoke. As tobacco smoke is simply warm air with a slight 

 excess of carbonic acid carrying solid particles along with it, the change of 

 properties at the surface of the cloud must be very slight compared with that 

 at the surface where two really different gases first come together. If, there- 

 fore, the phenomenon observed by Bosscha is a true instance of surface-tension, 

 we may expect to discover much more striking phenomena at the meeting-place 

 of different gases, if we can make our observations before the surface of dis- 

 continuity has been obliterated by the inter-diffusion of the gases. 



