liquid contained between two rotating coaxal circular cylinders 459 



Therefore p is of the same order as A, if A is large. Accordingly 



pcoa^^ / a^\i pWi^ ' + P') . (9^ 



fx \ b^J A 



tan sn = Vi^p^ + 2A'¥'^ - X^)l{^p'' + A) (10), 



s2 = 2py'{X^ + p'') -X^-p- (11). 



(10) and (11) are the same as Orr's (30) and (21). 

 (6) b/a yiearly unity; A not large. 

 We find s = p, sn = Itt/Q. 



(c) a and b large; b — a finite; A not large. 

 We have s = p, sn = pn = Ttt/G. 



Write b - a = d. 



Then » = log.(*j) = log.(l+^) = f, 



Ina 

 and P = -6d' 



= 394/A. 



This approximation may be compared with the calculations 

 given above for b/a = -1. If, however, we make a and b infinite, 

 the restriction of A to finite integral values is meaningless, and 

 therefore we cannot expect to deduce the results for shearing 

 motion between two parallel planes. 



