Mr Weatherbarn, On the Hydrodynamics of Relativity 85 



The velocity is therefore radial from 0, and kv is inversely 

 proportional to ?'^. The flow of matter per unit time across the 

 surface of a sphere of radius r is ^irm, equal to the rate of creation 

 of matter at 0. Such a motion is then that due to a source 

 of strength m at the point 0. If the negative sign in (o5) were 

 replaced by a positive one, we should have the motion due to 

 a sink at of strength ni. And finally the velocity potential 

 representing a doublet at of moment M and with its axis along 

 the unit vector n is 



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