410 



Mr Wilson, On Convection of Heat. 



Fig. 1 shows some of the isothermal curves round a point 



source calculated by means of this equation, taking Q = 4nrk and 



spu e x ~ r 



-£=- = 1, so that 6 = . 



Ik r 



Along the axis of x in the positive direction x = r and 



Q — . . , , consequently the distribution of temperature along the 



axis of x in the positive direction is the same as if the medium 

 were at rest, however great the velocity of the medium is. 



Fig. 1. 



The distribution of temperature due to a point source at the 

 origin when v = w — can also be obtained by Lord Kelvin's 

 method of point sources. The distribution of temperature due to 

 the instantaneous generation of an amount of heat q at the origin 

 in a medium at rest is given by the equation 



s P 6 = 



qe 



h 



d,(irk'tf 



where k' = — and t is the time elapsed since the heat was gene- 

 rated. If the medium is not at rest, but v = w = and u is 

 constant and positive, then it is easy to see that the temperature 

 will be given by 



qe 4 *'^ 



SP ° = 8 {irk'tf ' 



