PROPERTIES OF MATTER IN THE GASEOUS STATE. 
837 
Fig. 12 shows what the lines would be if A B were hot on one side and cold on the 
other, the gas being at the mean temperature and of unlimited extent. 
(2.) The distribution of temperature on an opposite surface, or containing vessel, will 
also affect the shape of the lines of flow. 
Fig. 13 shows the lines between two parallel plates opposite one another, the 
inside face, H, being hotter than the opposite face, C, while the gas and the outside 
faces of the plates are at the mean temperature of C and H. 
Fig. 13, 
(3.) The shape of the lines will also depend on the shape of the hot surface, and the 
nature of the surface as affecting the rate at which it communicates heat to the gas. 
Fig. 14 shows the direction of the lines for a cup-shaped surface, supposed to be 
uniformly at a higher temperature than the gas. 
Fig. 14. 
In all these figures the lines are supposed to be drawn so that the distance between 
any two lines is somewhere between s and 2s, so that the excess of pressure along the 
