182 Transactions of the Boyal Society of South Africa. 
In conclusion, I have to thank Mr. E. A. Herman, of Cambridge, for 
his criticism of the paper in its original form, as a consequence of which, 
while the results and diagrams are unaffected, I have improved the 
methods of arriving at them, in particular by adopting the method of 
conjugate functions in finding stream lines. '^I am also indebted to my 
son, Mr. J. E. Littlewood, for some useful suggestions, and to Professor 
Crawford, of the South African College, for criticism of the paper in its 
final form. 
