1276 
(22.1) is the equation of D from 0 to F in fig. 9. It is 
more convenient and numerical comparison with the complete 
equation shows that it is little less accurate to use only 
the first two terms of the expansion of (22.1) in powers 
of te 
x= Ot+ Bt, (22.2 
whe re a = ee B+l (22.3 
e=-550 [a B 4 25| (22.4 
The equation (22.2) fixes the boundary D. The boundary condi- 
tions on it are 
P(x,t) = P (0,0) (22.5 
Q(x,t) = Q,(x,t) (22.6 
Q, is given by (19.8) and (22.2). If the value of @, so 
obtained is put in (22.6), one gets 
Q(x,t) = 4, + at + aner, (22.7 
where aC 2 (toy + B) (22.8 
qy =-4p(2% 2 But 3) (22.9 
do = BY (3y -1) (2H =8 B+1) (22.10 
In (22.7) higher order terms in t were again dropped (the 
error was found to be small in this case, too). One also has 
P(x,t) = P(0,0) = Q (0,0) = i (22600 
The boundary conditions are most convenient in the forms 
(22.7 nd (22.11). 
ae pe 
