32 J. E. Moore — Electrical Discharge from the point 



The above described experiments would seem to demon- 

 strate the reality of the secondary discharge streams indicated 

 by the kinetic theory. The experiments also show that these 

 secondary streams do not take definite form until the pressure 

 of the gas (compared with atmospheric pressure) is very low. 

 This, according to the kinetic theory, is what ought to be 

 found. 



To examine the kinetic theory, as developed to explain the 

 conduction of heat through gases, for the purpose of determin- 

 ing whether or not this theory can be employed to render an 

 account of the form and action of discharge streams, it will be 

 necessary to call attention to the heat-flow lines from a hot 

 body immersed in a cool gas. Consider a spherical cup at a 

 uniform temperature, higher than that of the surrounding gas, 

 and at great distance from any other solid body. Heat will flow 

 from the spherical body to the surrounding gas along lines at 



every point normal to surfaces of equal temperature. Thus 

 these heat-flow lines will spring from all points on the spheri- 

 cal surface, normal to the surface at the point of departure. 

 Calling els an element of the surface of the spherical body, 

 n a normal to the element at its central points, and 9 the tempera- 

 ture, then the quantity of heat conducted from this element in 



r/f) 

 unit time, is k-j- ; where k is a constant, depending on the 



nature and state of the gas. If we now define n as the normal 



to any isothermal surface surrounding the spherical cup, and so 



dO 

 choose ds that k-j-ds — 1, we can divide the whole space 



